It is probably the hammer spring that is weak. The trouble is that those guns were made in several models, and the company is long out of business, so it is hard to find parts.
If you can remove the left lockplate, perhaps you can determine what is wrong. If it is the spring, you might find what you need from Gun Parts Corp. (www.gunpartscorp.com
); they have some Crescent parts, including some mainsprings.