Recent changes to glass (and stained glass) caused entities to suffocate inside them. Reverting those changes left this weird behavior where moving glass will still hurt entities, for one tick.
See this video for an example:
Comments
ZeNico13
ZeNico13
Still in 19w13a
Jack McKalling
Confirmed fixed in 19w13b
EarlyReflections
Fry
Confirmed in 19w12b