mariabackup and innochecksum detects page faults but all ok in application

Hi,

maribackup fails on multiple tables with: Error: failed to read page after 10 retries. File <fname>.ibd seems to be corrupted.
innochecksum finds errors on the same page, in most cases page 5.
I managed to make the problem disappear (using OPTMIZE TABLE for each affected table) but then to check I stopped the instance, ran innochecksum for all tables which again found corrupted pages. Restarted instance and mariabackup fails again.
No problem selecting data for all of the tables concerned.
CHECK TABLE .. EXTENDED: no problem.
Problem started on 10.5.5 (binary installation). Two instance on server.
Exported database and imported on the other instance: no issue, but still mariabackup fails and innochecksum as well.
Imported on an instance on another server (same OS): still same issue.
Upgraded MariaDB to 10.5.8 on the other server: mysql_upgrade ran OK finding no errors.

What did work was to import the dump on my Windows 10 Portable computer on 10.5.8.

UPDATE: imported on a Centos 7 VM with same redhat-release/kernel: so, I guess this is not a bug but rather something bad in the configuration of the other two VMs. Main difference is that there are two instances. Or maybe some specific configuration that makes it fail.

Tried different settings for innodb_checksum_algorithm to no avail.
Tried inreasing nofile to 100000 soft and 200000 hard and 200000 in mariadb@server multi.conf.

Did not see any message regarding corruption in error log.

Seems quite similar to MDEV-21109 with the major difference being that both innochecksum and mariaback agree on the corruption. That bug mentions "ALTER TABLE <tname> FORCE" which I also tried and which worked in some cases but not all (with or without export/import of tha table). But when I restart the instance corruption reappears.

Happens even on empty tables.

UPDATES:

• import database on another VM same Linux version, installed default. No corruption.
• on the original "corrupt" database I had to copy the instance to another file system, drop the database, and import

Best regards