Today I decided to play on the latest snapshot (20w17a) but when I created a map there were some grey stripes which was an issue hopefully mojang will read this and fix it.
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Thank you for your report!
We're actually already tracking this issue in MC-179858, 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.
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Were you in the Nether?