Problem with light texture showing up on prints.

Hello,

I am new to screen printing. I am printing using comet white.
Usually I do 1-2 pass, flash, pass again.

I have an issue some of the time.
It is after I print onto the tee, sometimes there will be like a very light kind of what I describe as wrinkly texture on the print. It is subtle and you can't feel it. Most of the time you can only really see it on an angle. It looks like a small crease or wrinkle here and there.

There is no shirt fibers coming through or nothing like that.

Does anyone know what this can be or ever experience it before?

Thanks!