gen_random_uuid key collision

Hello, I'm hoping someone might be able to shed a little light on a strange
situation I encountered recently.

I work with a postgres instance which has dozens (probably hundreds) of
tables which each have a column defined as "uuid primary key default
gen_random_uuid()".

Most of the time this is fine, but one specific table has recently started
repeatedly having inserts fail because of a unique constraint violation
involving the primary key. The table only has ~10,000 rows, but I'll
sometimes see two or three collisions in a single day. No other table (even
those with many, many more rows) exhibit this issue.

We're running postgres 12, so I believe the gen_random_uuid function is
provided by the pgcrypto extension, but either way it'll be the same for
that entire database instance, so I can't explain why only one table would
be having problems if it were due to a bug in the function. Also, since I
believe it just uses openssl (which we have linked) to generate random
bytes, the chance of a bug should be very low.

Anyone have any thoughts on this?

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