The mainspring power seems to have a problem getting through to the balance. That's a very broad diagnosis, this could have any number of reasons, from problems with the mainspring, all through the wheel train (wrong, dried out or contaminated oil, debris in the wheels) all the way through to the balance.
A non-authorised repairshop should be able to fix it, after all, it's just a watch. At least they could tell you what's wrong. Leaving it not running and with the mainspring fully wound shouldn't be a problem, but I would try to get it running again, at least to have some clue about what's up. Engage and disengage the chrono mechanism a couple of times, use date quickset (if any) to change the date a couple of times, rotate the hands forward through 24 hours and note if this is smooth or catching or grinding somewhere. Put a bit of forward pressure on the hands, shake the watch. If you get it running again try holding it in different positions and note if there is one or more where it runs continuously. All this could help your watchmaker determine the cause.
--
If I were to agree with you, we would both be wrong
