Hi and welcome,
First, validating a database checks all links and objects with their connections and always needs resources from the computer, and if e.g. there is almost no discspace left this is difficult. Before we put the database files up for distribution we validate them, so it is not needed to do this on your end as well (but you can, of course).
deleting the redundant files there
Please don't delete files in the database folder yourself to get rid of databases, but remove databases via openLCA's user interface. Some databases are quite big, the ecoinvent system process (LCI) versions each above 1GB, thus if you have little disc space and restore them often, this can indeed consume what may be left. Solution is therefore to remove the databases via the openLCA interface, and then restore only those you need.
And if this fails, e.g. because you may have now a somewhat messed up database folder, ask the admin to remove the entire database folder and also openLCA and then to install openLCA again (or do this yourself if your user rights allow, and then restore only those databases you need).