Mining restarts from the previous mined block. Is this normal?

After mining block #1019219, the block number was changed to the previous block number and mining started again in that block.
Explorer shows that blocks #1019212 to #1019213 took a very long time to be mined.
I don’t know if the operator is aware of this behavior, and I don’t know if it’s intended or not, so I’m posting it here.

Screenshot 1
Screenshot 2

It’s normal processes in mining. Blockchain continues with fork and healing.