All mob heads are gone and some blocks and items are osoe gone and got replaced by skeleton skulls with a 2 next to it.
How you reproduce this bug is by going into creative mode and go in to your imitore and go to the items tab and you can see that some items are replaced by skeleton skulls.
Thank you for your report!
We're actually already tracking this issue at MCPE-100251, so I will resolve and link this ticket as a duplicate.
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