jglsprings: Your Taurus?
No, it was my brother's S&W 36.
I do not know if the chambers were refinished or it was some "paint" that got its way into the chambers. In any case this problem is solved. I "cleaned" the chambers using a bore brush with a dremel (slow speed). Now the ammo feeds perfectly.
wogpotter: the bore seems to be fine, but the cylinder to frame fit & gap has been narrowed. The cylinder does not close nor rotate as easy as before. It improved with lubrication and some dryfiring, and hope it will get "normal" after some use/dryfire.