What to do if DAOS does not work properly after upgrading to Domino 11

What to do if DAOS does not work properly after upgrading to Domino 11

After upgrading some of our mail servers to Domino version 11.0.1 we run into serious problems with DAOS. After upgrading from Domino 10.0.1FP3 to 11.0.1 on RHEL7, DAOS no longer worked correctly and DBMT moved all attachments back into the mail, which of course required a lot more disk space and backup volume. First measure was to stop DBMT to prevent further movement. All measures we had taken like rebuilding the DAOS catalog did not help.

Intuitively, we suspected that DAOS has the impression that it can’t read and/or write to its drive, but we see that it does. (All NLO files seem to be created normally). The logs said:
The database /usr/local/notesdata/mail/xxxx.nsf was unable to write to file /usr/local/daos/0038/3982A6E960B06118C1258583003DE6AB5973982A.nlo: Release 11.0.1 ...
In preparation for the downgrade back to V10, we rather accidentally came across that the reason could be in the lost+found folder.

After some searching we found this 11 year old APAR:
https://www.ibm.com/support/pages/apar/LO41779

We removed the lost+found folder and DAOS works as before now. It seems like this is a regression that was reintroduced with Domono v11. Domino v10 behaves differently or has no problems at all with the same folder structure. Deleting the folder lost+found seems to be a temporary measure that allows you to update to Domino V11 without having to wait for the fix even when using DAOS.