How to reproduce

Step 1. Create a redstone clock with a sticky-piston attached to it.

Step 2. Place a redstone lamp on the sticky-piston.

Step 3. Place a power source next to the lamp and then remove it.

The redstone lamp should stay on as it keeps moving back and forth.

This will not stop when leaving and re-joining. However, when you go out of simulation distance, it will reset.