Villagers seem unable to open copper doors in 1.21.4. If a copper door they want to open is closed, they will open and close it in a single rapid double-action, and will then linger before finding somewhere else to go, possibly repeating this with other copper doors. This wasn't an issue in 1.21.3 and only became one when updating in 1.21.4. Affects a vanilla server I play in.

This doesn't seem to affect wooden doors, also, as we have another village with wooden doors where things seem fine.