Error: file with name manindex.irs does not exist

On a 2.2.16 version of OrientDB, we received this error on a query:

OStorageException: File with name manindex.irs does not exist in storage abc

That is the first time this error showed. Checked the database and there is no such file but after checking a few other databases, there seems to be no such file in general - also looked at OrientDB demo databases and the file isn’t there either. There are two manindex files (cpm, pcl) in each database being checked and that seems to be what is expected - created a brand new database and contained those 2 files only.

We also checked whether or not the databases contained the files for the indexes we generate and this was the case in each database that was checked.

Anyone has an idea on the root cause of this exception? To get passed it, we had to re-create the database.

Thanks