Good that there is another msm, since I missed the first one... No matter what you do, the trunk won't detach for some reason. The trunks jbeam is a modified version of the newer Pessima's trunk.
It seems to detach fine here. Are you sure you are not getting confused by the debug mode? You have to go to select the mode 'skeleton + broken' to see the broken beams. The first mode will only show all the beams, won't colour broken ones differently. If you mean it's hard to detach, try making the trunk's breakgroup a bit more fragile.
Aye, I tried only the '844tc', which doesn't seems to have that issue. The one in your video is '846td', which indeed has this issue. So, the difference is that the bugged one is using 'Trunk with Lip'. I think there is an error you are not seeing in its JBeam. What I did is copying the 'Trunk' beam section into the 'Trunk with Lip' beam section (As they are basically the same), and it's working fine. Also, I'm quite sure you don't need to make your file replace the original trunk jbeam, as you are already using your own body.jbeam
Yes, that must be the case then. The original jbeam is called tailgate.jbeam for the wagon, so nothing get's overwritten. Alright, thank you for all the help and thanks to whoever set the sedan featured!