I am getting weird issues, while restoring SP2010 sub-site from our old SP2010 farm to new farm through a full backup. The subsite on old farm had unique permissions. As well as the lists inside the sub-site were also having unique permissions. Now when we restored the sub-site on a new farm, it broke all the security permissions. Now all lists underneath the new sub-site were inheriting the permissions from their parent. When we tried to update the permissions manually, It was not doing anything when we clicked on the button to stop inheriting permissions.
Further, some of the lists on the site were using third party Cross Site Lookup Fields, as well as sharepoint's Lookup Fields. After migration of the site, it seems like the backup/restore process did import data values for all inbuilt lookup fields but not for the Cross site lookup fields.
Now to get the values for these cross site lookups, I imported these lists from source farm as LIST Template and recreated these lists. Now this time it imported the list with all the data values and with all site permissions (Thats good so far).
Now after this, there was another weird problem, I was able to remove the permissions from the new lists (that i created through list template), but i couldn't add the permission to the list. When I pressed the button to inherit permissions from parent, sharepoint gave me an unexptected error and whole site broke up. Entire site collection now locking out all users with 500 internal server error. Central admin unable to do anything with site collection. PowerShell commands do not work on site collection.
I searched from various blogs and sites, but didn't find any solution so far other than to restore the database. Any suggestion, how to resolve the issue ?