Hello You tube has only today notified me of your query. I apologise for the long delay in replying. It is always better to e-mail me via my website, www.pentaconsix.com The lens needs to be serviced. The lubricant has hardened and needs to be replaced. This is a standard procedure for a lens technician -- not a job for the amateur, as the lens needs to be taken apart, cleaned, relubricated and then reassembled.

If 1/125 sec does not work, the cause is almost always hardened lubricant. The camera needs a routine service with the old lubricant being cleaned out and then relubrication & adjustment of shutter speeds (if necessary). It will then work like new for years.

Sorry, Sergey, I do not understand your question. Please ask again with different words. The word "shed" is not the right English word. I don't understand the phrase "on the outside a little shed".

I wanted to say that the shutter curtain is not new

It does not matter if it is not new, provided it is in good condition, is correctly lubricated (not something for the user to do!!) and was adjusted when serviced, if necessary, to give the correct speeds.