Super sorry for the lateness of this reply 🙁
I have seen hlmv do some weird things before and the physics or simulated physics in hlmv have been buggy for me in the past.
What version of HLMV are you using? By that i mean for what game? CS:GO?
Was there maybe an edit done to the model to cause this?
Did Valve maybe push out an update?
What i would try if its an hlmv issue would be to delete the bin folder where hlmv resides (maybe even deleting hlmv itself is enough) and then in steam tell it to check the integrity of the local files for whatever games hlmv you are using and then let it redownload those files you deleted.
That may or may not help, might be worth deleting the whole game and re-downloading everything 🙁
Sorry I cannot be of more help, and since my reply is a month late you probably already figured it out. If you do keep having issues I can try and help by replicating the issue with your model.
/foo
