Active redstone signals are not restored properly on world load.
In the video below, before I restart, the redstone signals are active, propagating around in a very large circle. The signal correctly triggers both the redstone lamp and piston each time around the circle.
However, after save&exit + reload everything is broken. There looks to be at ~3 pulses running around the circuit now.
Potato quality phone footage: https://1drv.ms/v/s!AmZge0rbDU70gdMthOW-83DbB81EOA