Help with details to fix Omega series 7166159

Hello,

I discovered this forum yesterday and, while searching its threads, found out a question on a watch from Ashleynewhook, published in May 11, 2017 and replied by monsieur François Pépin, indicating it might be an omega encased in Canada.
I have a similar watch, silver tough, which I too inherited from my late grandfather, my late parents had it serviced and gave it to me some ten years ago. Recently I decided to buy a silver chain and substitute it for my wrist watch in their memory, but it stopped working properly the same day i decided to use it (bad luck).
I went to a local specialized shop but they told me that whoever serviced it in the first place damaged the pendulum (i do not know if it is the proper term in english) while substituting an axle, and that he had no parts available to fix it.
Generally, it will run, but either faster than required, or it will stop while still winded and i have to put it back by blowing gently on the mechanism.
I wonder if anyone could tell me more about this watch's model and where I might find parts I can use to fix it, or even change the entire machine while keIeping the casing.
Thank you in advance for any help.

Hello,

It looks like a 35,5 or a 37,5. I am not sure I understand the issue. But if the balance staff is damaged, you can find the part. But it will not be a cheap fix. You can also try to find a donor movement, but on these calibers, the staff are most often the broken parts on donors...

By the way, nice watch! Not very rare, but nice and in good condition.

Cheers,
François

I have read again the OP's post, and you are probably right!