Thanks for the clarification. Yes! I can reproduce it in TOS2.06!
I also had a quick look into the code and see nothing that jumps out to me that could cause that at this moment.
My first thought is: Laserball was written and compiled with an older version of GFA Basic - it was before I was even aware of newer versions. Maybe this old version of GFA comes from a time before TOS2.06 and therefore causes issues???
Bringing this old code to a newer version of GFA to check that point is a big task. So it is unlikely I will adress this in the near future.
Going for an older TOS is definitely a good solutiion. Sorry for this.