Old metronome to repair Maelzel Paquet with bell

Warning, this metronome needs repair! Very old metronome from the famous French brand Maëlzel Paquet, a metronome manufacturer between 1815 and 1846. The metronome is made of wood, it is complete. Here is its history: it worked (I have the video) and also had the particularity of having a "bell" function with a bell ringing that marks the beats, by pulling on a wheel. Someone bought it from me on the site, I sent it, but something went wrong during transport. When it arrived it no longer worked, even if externally it had not moved. The buyer sent it back to me, I looked at it, and it turns out that it still works very well, but to do this you have to manually hold the key "tight", because as soon as you release the key, it stops. So it is something that can certainly be fixed by someone who knows a little about it. I don't dare take it apart and tinker with it. For the rest, it is in good general condition for an old gentleman from the 19th century but has a few small aesthetic defects: scratches here and there, the graduations of the tempos that are fading a little, the pendulum that is slightly curved and a crack in the wood on one side. Underneath it has its three feet, but the number is erased. All this is visible in the photo.