How do i stop the system from automatically deleting files in a SharePoint share?

[jad17555]

I am network administrator for a theater that relies heavily on files from previous year's activities.  Since migrating from a local server to SharePoint, the system account has been deleting files over 2 years old.  If the files are restored from the recycle bin or re-migrated, they are still being deleted.  The default SharePoint file retention policy has been set to 10 years in the information governance section of the Microsoft 365 compliance tool.  

How do I completely stop this behavior?   It is very frustrating for my users to look for a file and have to go back to the old server to find it.  It is making the SharePoint implementation worthless.

[#2]

To my knowledge there is not a default setting in SPO that causes files over 2 years old to be deleted. What are you using for the migration?

[#3]

@Juan Carlos González Martín I used the standard MSFT migration tool.  The files migrated and looked fine until a couple of days later a system process came through and "cleaned up" the result is a folder structure with no files in it and all the files in the recycle bin for the share.  If I restore them from the bin, they stay for a few days then are removed again.  

[#4]

That's strange...do you have any filter configured in the SPMT?

[#5]

Nope - all files are migrated and stick around for a week or so before the system process "cleans up" Looking at the dated in the recycle bin for one of the shares, it looks like the process runs every 2 weeks (8/5 and 8/19). Also, I created and migrated a new site on 7/8 and on 7/15 all of
the files were moved to the recycle bin leaving an empty structure. The last modified date on the base folder was 5/2019.

[#6]

Mmm...worth to open a support ticket so they can dig into what might be happening here. I would also recommend to do a test migration using the migration manager to see what happens