Here is the way to correct the problem of the XLR insert sleeve coming loose and causing the battery door to "flop" around as shown below.
On the UCR401, push the XLR and sleeve until the sleeve face is flush with the battery door as shown below.Then tighten the allen screw. Don't overtighten.
The sleeves on the UCR201, UCR211, UCR411, and UCR411A are not flush. Push the XLR sleeve until the sleeve face sticks out 1/16 of an inch (approximately) as shown below and then tighten the allen screw. Don't overtighten.
Thanks to our service manager, Dean Slotness, for the pictures and explanation.