At this point and the way it is working, not working, I would find a reputable hvac tech to at least troubleshoot and correctly diagnose and then if possible, DIY the repair.
If it is intermittent, it can be hard to find and could involve a safety issue as well.
Just not something I can be sure of from here without being there to test fully.
An hvac tech could do that at each component throughout cycle to find the problem.
Don't want you to replace anything that is not needed.
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?