I have the same issue. I can add packs via a third party app, but cannot open/run .mcpack - I get "there are no apps to run this file". The third party app saves its files differently, so I've been unable to use that route. This is definitely about the game & not the packs.
Redesigning my villager trader hall, had several do this. Broke the beds with an axe, without first waking the villagers.
Mine triggered when I tried to change the mob crushing rule (from 24 to 8)