Certain (not all) PS1 locomotives refused to work with chopped wave transformers such as the Lionel ZW-L. I have one such example, a Premier K4, that was produced in the window of production time (1996-97) when this was an issue.
Worn-out rechargeable batteries scrambling PS1 chips was a much more common problem, but one that was more easily correctable. I have replaced most of my PS1 locomotives with BCRs.
Other than that, PS1 has been reliable, as has PS2 after the 5-volt board design was changed.
