Usually when a powered rail, detector rail or activator rail gets destroyed it sends out block updates to the blocks diagonally below it.
In 17w50a, when you have a powered/detector/activator rail and you push it away with a piston, then it does not send out block updates diagonally below it.
This can cause some blocks to get into invalid states.
In Rail before.png you see a contraption. If you flick the lever, then you get Rail after.png . In this picture the powered rail on the lower block is in an invalid state because it´s on even though it is not powered by anything. That rail should have been updated when the upper powered rail was pushed away, but it wasn´t.
(Also this is not a duplicate of MC-96224, because the bug I´m describing here was newly introduced in the 1.13 snapshots and didn´t exist before, while MC-96224 is older, and secondly this bug is about block updates missing when a rail starts being pushed, while MC-96224 is about block updates missing when a rail finishes being pushed).
This affects the following situations:
- powered rails do not update their powered state
- stairs do not update the shape
- fences/walls/glass panes/iron bars do not update connections
- support requiring blocks do not drop
- gravity affected blocks do not fall
- activated detector rails do not unpower redstone dust
- redstone stays attached to wall