Help diagnose my pam 111

[metalzeus]

I have a Pam 111 and its been working fine.Lately when I wind it around 40 turns I can hear a "whizzing" sound like a short unwinding movement and feel it.I tested it and i can only get 17-19 hours .What do you guys thing it could be.Should I tighten the screws or can it be the mainspring slipping.Any Ideas or anyone that has this problem?
Thanks in advance.

 

[Strodda]

Definitely sounds like a mainspring issue.

 

[Retina]

Mainspring issues, might be a problem wth your main gears catch not catching correctly as well. Over tightening the screw is not the best way to deal with it, I would send it to a local watchmaker

 

[Raddave]

Mainspring slipping inside the barrel

 

[metalzeus]

Ok thanks guys.I'll have check out