While I was recently out traveling the Prontar shutter on my Super-Angulon 121 began to stick. First it began sticking open at the 1 sec. setting and then progressed up to the 1/4 sec setting. So I either shoot at bulb or faster than an 1/8th. Is it worth getting the shutter repaired (assuming it can be) or should I junk it and buy a new shutter?