I have a TS 55 and TS 75.  I use the 55 frequently, the 75 very rarely.  I have had the 75 apart previously in an attempt to calibrate to the same splinter guard cut line as the 55 (I was unsuccessful at doing this).

This weekend, I was cutting into a glued set of (3) 2x pressure treated material.  While cutting on the rail, I could plunge my 55 to full depth and move forward in the cut without a problem.  Nice and smooth.  When I tried the same with the 75, the saw would bind and jump backwards dangerously.

I know PT generally binds if you cut it straight from the lumber yard.  However, this PT had been drying for several weeks, and was probably in the 18% moisture range before I used it.  It was machined to S4S prior to cutting, as it was part of a large arch glue up.

Would toe in/toe out problems with the 75 cause the binding and jumpiness?  If so, how would I check and fix without sending it in to Festool?

Make sure the saw is up to full speed also. That was the only time I’ve had that happen.

Your subject seems to answer this, but let's clarify anyway.  The saw is kicking back during the plunge itself but before you actually move the saw forward?  If that is the case, it's probably your technique.  The larger blade in dimensional lumber will have quite a bit more contact area with the wood during the plunge compared to a 55 saw.  Go slow, particularly if you're using the crosscutting blade while ripping.  I use the little anti=kickback do-hickey on the back of the saw base even when plunging into 3/4" ply with my 55.  I would use that here assuming the 75 has a little notch on the back of the plate to receive that. 

If the kickback occurs after you plunge and while you begin moving forward, I would look at toe out.  Skim the edge of the board and look for striations that match the direction of the circular blade profile on the back edge of the blade.  If they are pronounced, it may indeed be toe'd out. 

Agree with @RKA  Do you have enough runway to get the 75 fully plunged before cutting? The larger diameter blade changes the geometry of the kickback potential from down and back to almost fully back.

Plunge slowly and either use the stop block or literally clamp the saw/rail/work together. You might also maximize the cutting depth to change the kickback geometry to pull the saw down instead of push back.

I agree with Michael and RKA.  Are you using the guide rail that came with the TS55?  If so, it is too short for the TS75 for some wide cuts on sheet goods.  A longer rail would allow you to start the saw without plunging.  Otherwise, use the stop.

This isn't a tool issue and I have moved it out of the tool problems area.  The TS saws and frankly any circular saw can kick back when plunged.  The TS saws come with a stop to place on the rail to control this.  The TS-75 has more torgue than the TS-55.

Peter

Especially given you have adjusted it unsuccessfully before I would start with checking toe in as per the TS 55 supplemental guide. Assuming you have feeler gauges it’s easy to check but a pain to adjust.

If the back of the blade is contacting hard it will cause the saw to lift as you plunge.

The difference in cut (perceived saw effort, lack of burning and also smoothness of the cut face) when properly aligned is huge.