Zenit C Problem with 1/25

I recently won a Zenit C off of the auction site. All is good except for the 1/25 shutter speed which operates as if it is in Bulb mode.

Any ideas of what may be causing this?

The mechanics are slow due little use or long rest periods.
simply try to lube the curtain axes with WD 40 or similar.
Use the long stripe to reach the pivots and ball bearing.
Avoid moisten the curtains.
Regards LP

I don't think the problem is a sticky curtain. If I hold the shutter release down, the shutter stays open. When I release, it closes. There's nothing sticking.

Is the shutter speed knob screwed on correctly? Sometimes if slightly loose it can move around so that the speed you are selecting is not the one it should be , e,g at 1/25 it acts like B setting- does the B setting also act like B or is it different too?. If so there are 2 grub screws that hold the knob on- try loosening them and shifting the knob around til it is in the right place then tighten it back up. I have found this hapened on a couple of my early Zenits and a Zorki 4

Samsung GX-10,too many Russian Lenses, A lot of Zenits, an Almaz 103 a few Yashica,and finally a Minox35GT

Yes, in effect I have 2 bulb settings. I'll try it and see what happens.

That didn't work :(