1. Drop Board
When the hashboards error of the miner unable to trigger the miner protected mode (Eg. Unable to locate the board, datalog unable to detect any error while function and etc.), and the miner is able to run with fewer boards, it means the miner is low hashrate.
Solution: Please try to reconnect the cable, but normally it requires to return for repair.
2. Abnormal Frequency
After repairing the miner (replaced EEPROM or PIC etc.) or repairing the single hashboard, the frequency of the hashboard might be changed, which will cause the frequency different from the original setup, the miner running under low frequency, which cause the low hashrate of the miner.
Solution: Generally this problem would not impact the normal use of the miner, but if you need it to restore the original hashrate, it requires to be returned for repair.
3. Instability of ASIC IC/ Aging
The miner can operate as usual after turned on, but the single hashboard shows 0 hashrate after running for a while, or the hashrate of the miner is lower than the standard hashrate (normally fluctuation around 5%), but is able to function as normal, the defect rate of the hardware will significantly higher than the other 2 boards, which means the ASIC IC might be unstable or aging.
Solution: If it would not impact on the normal function, it is recommended to use it; while it is suggested to return for repair if impacting the normal use.