Have you tried to disassemble this TG? I notice in the picture there seems to be a lot of clearence around the trigger pin. I'm talking about between the pin and the housing. If you have an accumulation of clearence (wear) it seems possible for there not to be enough movement in the trigger to relaese. Most of the problems I have seen with TG are the result of people trying to "improve" these mechanisms. You said this one is from storage, so I guess you have another one to compare it to. There are several good videos online showing how to disassemble and reassemble these things, but if your not comfortable doing it you may want to find someone to help you. I don't have any idea how hard that would be in France.