So, it says there's a stack overflow in 19, I have a GOSUB later in it to @PKMBTLSYS, to stop an infinite loop to a part that shouldn't yet be accessed, so, what exactly is wrong, and if you can help, how can I fix it?

Well, any GOSUB needs a RETURN.

As Pkyoshi19 has said, a subroutine which can be called by GOSUB has to be followed by RETURN. RETURN removes a program counter which has been stacked by GOSUB from memory. However GOSUB without RETURN keeps memory stacking and stack overflow will occur soon.

In this case, I guess you should apply GOTO instead of GOSUB.