Have you tried to see if it's the actual control vinyl themselves? Do you notice any obvious scratches/scuff marks? Take note of the location on the vinyl where the track(s) skips and check it for defects around that area of the vinyl.

The SL4 doesn't work like the SL1, the SP-6 can only be routed out one of the outputs on the SL4. Well, you can set each slot to a different output, or if the slot(s) is set to master then it will go out whichever output you have selected as the master output. Since the SL1 only has two outputs, your only choices were L (left), R (right), or M (Mixed, or both LR). The SL4 has much more outputs and sending the SP6 to all the outputs at once wouldn't be good.

yes i have tried the vinyl i tried 3 differnt sets 2 of them brand new and brand new needles too, and it doesnt happen in internal mode but in relitive or abs mode it hapend with the sl1 & sl4

I still need help please ?? i have 2 days to figure this out

Is this happening on both the left and right side?
Do you have a cd player you can test with?
I ask because cd players don't have all the problem spots that turntables do.
When testing with a cd player you'll want to make sure to change the audio input setting to line in either the Hardware tab (when using your SL1) or via the dipswitches on the input side of your SL4.
Once done, play a cd in the cd player and see if you still get the bad tracking.

Also.. make sure your not plugging the SL4 or SL1 into a USB hub or splitter.
It needs to go directly into the computer.

If everything works with a cd player than the issue is going to be coming from your turntable(s).

still dropping time code signal and i have noticed that the louder the music the more fuzzy my circles are

Did you try testing with a cd player yet?

This is going to rule in/out an issue with your turntables.

Yes and it worked fine with Cd players. its weird because it will just randomly happend on the left and right side like it will be playing fine and then i will get a little red than alot red. I pick the needle up to clean them place them back on vinly than i get staright lines in scope view than i turn both tables off and back on than i get good circles. SMH !!! could this be bad grounding ? and if one table is not grounded correctly could that affect the time code randomly dropping on both tables ? also i just noticed one of the RCA'S on the left table has a slight splice in it but all of the wires seem to be intact inside ? so could 1 bad RCA affect both tables ?? this problem is so frustrating ive spoke with Serato for 4hrs had 8 Dj's look at my setup and still no one has a answer !! and lastly could to much music on my computer or low ram be the reason why the timecode signal keeps dropping ?

If CD players work than the issue is definitely coming from your turntables.

First I would try switching needles, making sure the wires are connected correctly on the needle/cartridge, and clean the inside of the tone arm(s) with some rubbing alcohol and a Q-Tip.
If that doesn't work than try to jiggling or crimping the rca cables to get a good connection.
Worse case scenario you'll need to get your turntables serviced and have them put new rca cables on the decks, if you used turntables with rca cables that are hard wired to the TT.

Unfortunately this is REALLY common with turntables.

but could the bad "Grounding" also be the problem ??

oh ya.. sorry.. a bad ground can definitely effect the audio signal.

If their is a short in the ground you should be able to jiggle the ground cable and hear the audio go wonky.

If you find that that is the case I would get your turntable repaired and get a new ground wire soldered onto it.

Still having same problem (seems like its a grounding issue) but my Turntables both sets New and used tables have been grounded to the mixer. I have tried new RCA cables from the tables and from the mixer.Ive tried NEW vinyl NEW Needles NEW slipmats smh !!! and it doesnt happen all the time but when the music is loud and the base hits my circles get fuzzy and red bar seems to be more red. I tried pressing the "Estimate" buttom and both sides mostly jump to the right (thats why i think its a grounding issue) but everything is grounded. I HAVE TRIED EVERYTHING !! even swapped serato boxes and it still happens the only other thing i could even think of is maybe i have a short in the power cord to my Laptop, But whould that cause the Time Code signal to Randomly drop or not show at all ? and also sometime the circles in serato will spin in the opposite direction (even with it hooked to properly ??) I tried CD players and it worked fine. Like some events it will work with maybe 20 percent red than other times when i plug in i get NO time Code at all than with out touching anything it will pop up to about 80 percent. My PC is low on memory and is about 5yrs old but the problem came out of no where ??? PLEASE HELP !!! im ready to just throw this whole setup out the window and quit being a DJ lol smH

Ah sorry man:(

From what you're saying it definitely sounds like an intermittent issue coming from your turntables.
Once again.. cd players are working fine which pretty much narrows it down.
Also, you're saying that sometimes the virtual deck spins backwards... this means that the signal coming from your turntables is getting inverted. This will reverse the control tone and get the virtual deck playing backwards.
This is also a red flag in regards to a short coming from the turntable.
The problem spots on turntables are the height and weight of the tone arm not being set correctly depending on the type of needles you're using, a bad connection in the wiring on the cartridges, a bad connection between the tone arm and the cartridges (try cleaning the contact points with rubbing alcohol and a Q-Tip), a short in the tone arm, or an intermittent short in the rca cable coming from the turntable.
If you've tried brand new needles and vinyl than try cleaning the contact points and jiggling the rca cable coming from the turntable.
If you have a short in the rca you should be able to get a shoddy tracking signal by simply jiggling the rca.

Also.. in regards to calibration...

Play music as loud as your going to be playing throughout your set.
Put the needle on the turntable with the platter stopped and hold down the estimate tab for about 5 seconds.
This should automatically set the threshold to where it needs to be depending on the environment that your in.

When your in your bed room playing on a smaller sound system you should get a lower threshold setting although when your at the club playing on a large system the threshold will typically jump to -24.

The most important thing to look at is the number in the upper right corner of the scope view while the needle is on the record and your platter is stopped.
If this number is fluctuating then your going to be picking up interference.
You can also adjust the threshold manually by simply dragging it to the left while looking at the number in the upper right corner.
You'll know you've gone too far to the left when that number starts to fluctuate.
At that point, drag it one notch to the right.
That is the perfect threshold setting for the environment that your in.