Compressor intermittent. Heat pump A/C.

I've got a Tappan branded 3 ton heat pump that's giving me fits this year. For the past week when temps finally hit summer norms the compressor has stopped turning on in the afternoon/evenings. In the mornings it works great but when it doesn't, the outdoor fan blows for hours, the outdoor air and big line are ambient, and the indoor air is the same as the indoor temp. A tech came out the other morning (again, mornings work fine) and couldn't find anything wromg but after i paid (for nothing) and recalled the next day saying it was still not working they thought the compressor was going out (over the phone diagnosis). I've also been told that compressors either work or don't, they don't do intermittent.

I was wondering if a new capacitor and hard start kit might help out with what i am experiencing? I also installed an ecobee smart si during the heating season but since the a/c works at times i don't suspect that to be the issue.

Model: ft3ba-036ka

Capacitor: replacement for 620779. ~$20

Hard start kit: CSR U1 by Five Two One inc off of Amazon. ~$35