I believe this has been resolved. Please close the ticket
Yup, got that too. The one formation (1.13) went away by itself when we upgraded to 1.14. But a new one formed in a different spot. Now, with 1.14.1 that one's gone, too. Probably moved somewhere else. ALIENS!
I saw this on a mooshroom biome. A mooshroom was very diligently trying to get onto a barrel with a half slab on top.
I had the same issue. Then I remembered I had the issue before. To fix it, I had to go into my advanced internet options and enable 'Use TLS 1.2'. Sorted it out immediately.
PS. I also enabled 'Use TLS 1.1', so I'm not sure which one fixed the problem, but I think it was 1.2
Tested in v1.21.43. Can confirm that this is resolved