Well, the most likely problem is the contact with the tact switch inside. You mentioned that a brass pin on the top of switch section is loose (goes up and down). Is it spring loaded? Has a resistance to it? It seems like Indulgence went
thru a few versions and it is hard to tell from the video which one exactly you've got. I'll try to take a few shots of different versions and post it here so you can compare. Anyway, you can easily un-screw the bottom part by using two holes and you'll see the tact switch and the contacts. It might be that just un-bending the contacts a little bit will be enough to fix it. If you have a multimeter and can test the tact switch would eliminate the possibility of a bad switch.