My first vintage :

[Microbus99]

the brackets would solve your problem.. i would have to agree put in some glass and your good to go.. but all we can do is see it, your the one that can see it an feel it..

take the machine out of the case.. undo all the original corner brackets then see if u can pop the corners and get some good glue in there then reasemble.. if u think u need it u could add the corner brackets

good luck to ya

Thats what I was going to suggest as well. Reglue the frame together. Dont be afraid of it. Just study it for awhile and take alot of picture before disassembly. Also dont be in a rush either!!