There are some chunks that are ignored by the cave carver leaving sudden giant cubes like the one in the picture. It isn´t really that rare and it ruins the immersion.
Seed/coords from 21w13a (from MC-221692):
Seed: -9096957297348170478
XYZ: 240 -50 -610
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However, this issue has been temporarily closed as Awaiting Response.
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Probably the same issue as MC-7200
Reopening as there are now three other tickets describing the issue. I added seed/coords from MC-221692.