See post #8 for a link to it.
Baomain brand.
That’s my primary suspect in this mystery. ?
First I checked fuse time curve.
Then I looked at the fuse holder.
How about a picture of your cables connected to your fuse and your fuse holder?
Wires getting hot just near the fuse indicates heat is generated there.
Here's what I'm hoping to find out is the problem:
Because that fuse holder doesn't have separate stud for cables, the fuse and the cables are on same stud but with >something< between them. If that something is anything other than copper, say a nut or washer of other material, it could be a high resistance connection.
I prefer separate studs/bolts for wires vs. fuses because then I can unbolt fuse without risking a flying wire coming lose and shorting somewhere.
(Yes, 2/0 is good for well over 200A if individual conductors in free air, for cooling. Just in cable or conduit it's about 200A. But as you say not hot so it's not the problem here.)
I think you have a 6kW inverter. 300A at 24V is 7200W, not enough for inverter inefficiency and 25% headroom to avoid nuisance trips. So shouldn't be run full load continuously. I now add 12% more headroom due to high ripple current.