It probably stopped hashing because temps were high and the miner went to protection mode, times like these are where reading the kernel log will most likely tell you the exact the problem , but instead you went ahead and flashed a different firmware without having figured the cause.
however , I am not sure how did the LPM firmware allow you to hash with a faulty fan, before it start hashing it has to test both fans for a little while and if they are under about 4000 RPM it will show a fan error and won't start hashing.
I would also inspect the fan grill , I had some bad grills slightly touching the fan motor causing the fan to run slower and wear out way too soon, this can be fixed by removing the grill and bending it a little bit to the outside to allow more room for the fan motor not to touch the grill.