When mining a lot of blocks in a small period of time the game creates these invisible blocks which can only be removed by leaving the world, once you join back the invisible block becomes into a normal block which you already mined. This issue is most common in the nether where you can mine blocks in an instant and even more common if the block that your're mining has ladder on it.
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Thank you for your report!
We're actually already tracking this issue in MC-156852, 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.