I was playing around in the new snapshot, and there seems to be something up with Item frames whenever gamerule doEntityDrops is false. They become invulnerable because they cannot drop their item, causing them to be only "kill-able" with commands.
I know this is only a minor issue because you have to have cheats enabled to cause it, but it is a bit of an inconvenience.
Thank you for your report!
We're actually already tracking this issue in MC-130558, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
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