Is there a time limit on choosing heads or tails

How do you know that the specific player in question didn't have a bug with their computer or client? File corruption, network issues, etc.

How do you know that it wasn't all just an unfortunate coincidence and that the bug only happened to manifest when you played a certain player?

Describing the software acting irregularly, especially when it is known to be bugged, and claiming that as definitive evidence of some kind of malicious hacking is somewhat presumptuous.

Again, you may be entirely correct.

My main contention is that you should be careful making accusations of malicious behaviour when another rational explanation is known to exist.

That goes double for the people posting usernames.