MTH F-3A PS1 won't shut down

What is your power source for the track?

You might have a voltage "leak" where track voltage is really never going fully to 0V. The lighted lockon was a good idea but may not solve all voltage leak situations.

Otherwise, could be a conflict where the sound chip VS the specific PS1 upper board and it's firmware are a mismatch? Just trying to come up with a software (firmware) reason that a reset did not solve.

What does it do if you lift it completely off the track? Does it then shut down?

Some very early units had a battery on off switch, but not sure it would allow movement just keep sounds active.  They would periodically make sounds again.  G

@Vernon Barry posted:

What does it do if you lift it completely off the track? Does it then shut down?

Vernon's hit it on the head.  Lift it off the track and see if it shuts down in a normal fashion, or just plain quits immediately.

Mike