system monotoring - what to monitor?

had a couple of freezer problems lately and lost a lot of stock

I've set up a tiny esp32 computer with wifi (it's about the size of a thumb) and a bunch of DS18B20 twmriture sensors - the temp sensors are cheap and the little computer board will support hundreds of them

I've set up homeassistant running on my server (server was running anyway_ so that records all the tempritures, makes graps etc. etc. (all free and easy)

instead of just monotoring freezer temps I'm thinking I should monitor more....

evap air in temp
evap temp
evep air out temp
liquid line into evap temp

adding some other sensors I can check what's going on, freezer on/off (we have on/off switches at the door) defrost on/off, I'll check for power going to compressor too, to check and see if it's running when it should be / hasn't tripped out

I'm going to add a screen in the tea room showing tempritures, so we can track what's going on (there's 6 freezers used as blast freezers - fresh/ambiant product in)

not setup yet but I'be ordered coulour changing led bulbs, and I'll be able to make them automatically change colour to match freezer tempritures... a nice easy display in the factory for everyone to see

I think I'll add an extra single bulb next to the factory door to glow red if any freezer is turned off - so it's easy to check on them before leaving for the night

anything else anyone thinks I should monitor? I could add pressure monitors to liquid/suction lines... but that seams a bit overkill... all the other monotoring is non intrusive