|I see your problem now, but have no solution.|
Sometimes you have E: plugged in, the SR starts monitoring it,
then may create a Restore Point at some time later.
Then sometimes you have E unplugged, then monitoring of E stops. But then maybe all Restore Points give reference to E drive. Then you want to use a Restore Point, and you can not.
I am going to have to check that out with a new Flash drive I just purchased.