Got a little problem on my server, since like 2 days items frames with an item inside are completly indestructible, you can only destroy them by destroying the block there on. I'm not sure which plugin is causing this, important plugins on my server are ; Essentials, mcMMO, WG, WE, WB, LWC, Craftbook, AntiCheat, LogBlock, PEX etc. I didn't update anything in the last two weeks, so i have no idea where this is coming from.
if you have world guard look in the config and make "block-item-frame-destroy: true" change it to false