many backends hang on MultiXactOffsetSLRU

Hi experts,
we have a Postgresql v14.8 database, almost thousands of backends hang
on MultiXactOffsetSLRU at the same time, all of these sessions running same
query "SELECT ....", from OS and postgresql slow log, we found all of these
query on "BIND" stage.
LOG: duration: 36631.688 ms bind S_813: SELECT
LOG: duration: 36859.786 ms bind S_1111: SELECT
LOG: duration: 35868.148 ms bind <unnamed>: SELECT
LOG: duration: 36906.471 ms bind <unnamed>: SELECT
LOG: duration: 35955.489 ms bind <unnamed>: SELECT
LOG: duration: 36833.510 ms bind <unnamed>: SELECT
LOG: duration: 36839.535 ms bind S_1219: SELECT
...

this database hang on MultiXactOffsetSLRU and MultiXactOffsetBuffer long
time.

could you direct me why they are hanging on 'BIND‘ stage with
MultiXactOffsetSLRU ?

Thanks,

James