When I wanted to work on some of my command block contraptions today, I came across a strange bug. At first I didn't know what it was, so I looked at the crash log and found it had to do with comparators powering activator rail. After I did some testing I found that it only occurred when a comparator powered an activator rail or a powered rail and then unpowered. The game crashed and the activator rail stayed on when I restarted the game. In the attachments are the possible set-ups to recreate the bug. Strangely if the comparator powered the block above the rail the game wouldn't crash.
I have no idea what this might be and it doesn't occur in any previous versions, not even the previous snapshot.
It is not a hugely game breaking bug and shouldn't be top priority, but it is quite annoying when trying top update pistons, like I did.

p.s. After the game crashed about three times my save file disappeared from the UI in game, while it remained in the .minecraft saves folder. Is this an intended feature?