1. place colored signal rail
2. equip yourself with signal
3. get into the cart and stop on the rail
4. -- Now, either unequip signal or exit minecart--
5. The powered state of rail is stuck on ON when it shouldn't be

This is only occurring because the minecart is stationary. I encountered this during development and sadly there is no easy fix. Most likely this will never be fixed.

What about detecting player triggered events?

• player dismounts a cart - force recheck of rail
• player scrolls through the EQ - force recheck (it turns out, that when you switch equipped signal when stationary it just updates to ON, but never to OFF)

I think that solves 99% of cases. Other 1% are probably some edge cases when player logs out, is somehow forced to dismount etc. but they should appear rarely and can be done later.

Good idea, that would work. Is there a particular use case you need this for? I may fix this with the next patch, but probably not soon.

I don't particularly need it fixed ASAP. No stress. Just thought it would be good for consistency.