I have a Montana 4540, bascially same loader/frame as yours. No, I haven't had any come loose, but I'm going to check them again, now that you have.
I did have 2 of the main FEL bolts shear off while pushing a big pile of brush in a low gear. /forums/images/graemlins/confused.gif
I've said it before and I'll say it again, The Montana 4540 has enough power to hurt itself. The 4540 engine should have been put in a bigger/heavier frame tractor.
James