Eric at Garand Gear has some excellent info about inspecting & trouble shooting a Garand. Just some of his links that may hold the answer to your rifle's problem are:
M1 Garand (Part Inspection) (particularly the part about the bullet guide)
M1 Garand (How to Strip your Rifle)
M1 Garand (Failure to Cycle)
M1 Garand (En Bloc Clip Problems) (especially the part about the weak clip latch spring)

In my experience, a weak clip latch spring was the cause of problems similar to what you have. Replacing the CLS ended the problems. An expedient solution is to add a "helper" spring to the CLS. Take the spring from a BIC butane lighter that pushes the flint against the striker wheel. Cut it so that it is about .1" longer than the CLS. It is thin enough to fit inside the CLS. Install both & see if it makes any difference. Good luck!