I am not a gunsmith but I do own an older BLR and I can't imagine how this would happen unless something has broken or failed inside the rifle. The only other posibility is that a foreign object is preventing it from working properly. You could try and use a proper solvent and compressed air to blow out any object in the action, but other than that it would require disassembly and inspection if something has failed.
Again, I'm not a gunsmith and I haven't heard of this particular problem before, but maybe someone else has.
Best wishes,
fish head
