As i've found this issue happened in 1.14 already.
Looks almost as if every second stripe of blocks is affected.
Also spawning behaviour is weird. Not sure but could possibly be the same issue.
MC-181285
Rain, snow and burning mobs underground
Resolved
Duplicate
0
Thank you for your report!
We're actually already tracking this issue in MC-179845, so I resolved and linked this ticket as a duplicate.
However, that ticket has already been resolved as Fixed. The fix will arrive in the next version or is already included in the latest development version of the game.
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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