Autovacuum Hung Due to Bufferpin

I have a very small table of 28 rows that is less than 10kB. One of the AV
workers has been stuck autovac'ing it for over 20 hrs now with no progress
in heap blocks scanned or vac'd. I terminated the AV worker and ran a
manual vac which also ended up stuck waiting for a bufferpin.

pg_locks shows no blockers while this is happening. This view shows a
constant 13 sessions running SELECT statements on this table posting
AccessShareLock. Of course, these is also the AV sessions
with ShareUpdateExclusiveLock

I have also disabled AV for the table, but AV does not appear to honor that
due to 'to prevent wraparound'.

Why is AV blocked by bufferpin given the fact that this table does not get
an DML changes. It is purely read only. What can be done to resolve this?

----------------------------------------
Thank you