Hi Jean-Paul,
This looks like the same DB_STORAGE_DEGRADATION / RejectedExecutionException errors as discussed in Canton participant node warn message: DB_STORAGE_DEGRADATION.
The extra log line
WARN c.d.c.r.DbStorageSingle:participant=PARTICIPANT_NODE_A tid:990c167a76d0bcc45c141f0cbb568f2a - Now retrying operation 'com.digitalasset.canton.participant.store.db.DbContractStore.storeElements'.
is saying that the database operation “DbContractStore.storeElements” is being retried as the database task queue is currently full.
Let me know if the fixes from the other thread don’t help you.