Occasional no start on 94 850. Any Advice?

[Constantine8020]

I have been daily driving a 1994 Volvo 850 non-turbo for a year now and for the most part have experienced no issues. Occasionally though, the engine will fail to start. Sometimes it will hiccup while cranking like my timing is off, other times it will crank indefinitely and never once even try to start. This almost always happens once the car is up to temp but has once or twice happened on cold starts. I had the camshaft position sensor changed about 8 months ago which seemed to make it run a little better but the problem persisted, and I have taken the connectors off of both the cam and crank sensors and cleaned lots of corrosion out which seemingly helped until it recently died on me again. Once I let the car cool down fully (or more realistically get it towed home) it starts without a problem again, leaving me fully stumped. As time goes on the issue seems to happen more often, in the first few months of ownership this never happened.

My OBD1 codes are;

A3: 213 and 214 which I believe to be my rear wheel ABS sensors, unrelated but not sure what that's about

A6: 324 and 214 which are camshaft signal intermittent and VSS signal intermittent. The car is an automatic and has no trouble shifting so I think the VSS is a problem for future me, but the camshaft signal is the one that catches my eye

and B2: 122, which from what I have read online is a cruise control thing and can be safely ignored.

A nearby mechanic thinks there might be some fault in my ECM causing it to lose signal intermittently, but I'm not sure. Would a faulty cam sensor cause a no-start when the crank sensor is throwing no errors? Could it be an electrical issue between any of the sensors and the ECM? Some longshot forum posts suggest an engine coolant temp sensor, but it is throwing no codes and the bolts in my thermostat are stuck tight so I haven't been able to test its resistance.

I know this is a huge write-up but this issue has been beating my ass for months now and as this is my only car and I am a poor college student I really need it to start being reliable. Any advice would be appreciated.