Hey guys, Im having trouble making a straight cut with my track saw while bevel cutting.
  When I've got the saw set to 45 degrees I'm consistently getting a slight arc to the cut line.
  However, when the saw is set to 0 degrees the cut line is straight.
  I've tried clamping the track and also with no clamps and the results are the same. I get a ~0.5mm gap at the center of a cut when a straight edge is held up to it.
  Anyone else have this issue?

Try putting your left hand on the base that is over the rail while making the cut.  The weight distribution when the saw is beveled over can make it harder to make it lay flat on the track.  If this works for you and you plan on making many bevel cuts then the Parallel Guide might help.  That is the accessory that looks like an edge guide.  If you mount that upside down towards the motor side of the saw it will register on top of your work and give you a safer place to apply the pressure.  If your workpiece to the right is large enough you can mount it to the right and it will prevent tipping.

Just a couple of thoughts.

Peter

Yeah, I press on the base plate for this.

But thank you Peter for making me realise the parallel fence can work upside down, over the rail, on the motor side, while using a track. . . . I'd never have thought of trying that on my own
I think owning the makita as well would have kept the concept for my mind as that saw won't sit on the guide rails with the parallel fence installed. . .

As your curve is appearing only when doing bevel cuts: Lifting the saw at a 90° cut will not move the kerf position (but only reduce depth), but as the blade is tilted on a bevel cut lifting the saw then (with or without the rail) will lead to the kerf position chancing (moving toward under the rail, instead to staying at the splinger guard).

Lifting only the saw but not the rail also leads to the splinger guard being cut in the wrong geometry, you can check for that by standing the rail with the splinter guard on a flat surface.

Gregor, can you explain this a little more? I think I’m having this issue but I don’t totally understand what I might be doing wrong.

For me, when doing a bevel cut, the first inch or so isn’t cutting to my line - it’s a tad shy - then the rest of the cut is on point. I had also noticed that it seems part of my splinter guard is cut slightly differently, which is leading me to believe it might be this “lifting” you’re talking about.

On my cuts, I pass the saw through with the stop on to break through my plywood veneer, slide the saw back and cut at full depth. I’m holding my left hand on the base the whole time to keep the saw level. So I’m not sure where I might be “lifting” but maybe I’m missing something..