Okay, today I wanted to check out the new update/snapshot (20w17a) and when I logged on it was raining through the mountain and into my house underground. It appears to only work on stone (I haven't tested every single block).
I tested and if you place any other block, for example, tnt it appears to have stopped the glitch/bug.
Thank you for your report!
We're actually already tracking this issue in *MC-179845 *, so I've resolved and linked this ticket as a duplicate.
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, you can check the Fix Version/s field in that ticket to learn more.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
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