You can try to run the hashboard with a different (higher) frequency with Braiinos
Do you mean higher voltage? because usually that is the case, many hashboards will need lower frequency or/and higher voltage to run stable, higher frequency cases issues even to stable hashboards.
OP, since you like fixing stuff, the issue with that bad hashboard is kind of straight forward, the kernel log states
driver-btm-c5.c:13522:bitmain_c5_init: retry Chain[J7] has 15 asic
This means that the test signal stops at chip 15, it either reaches there and doesn't move to the next one, or simply just doesn't get there, so you are going to need to check chips 15 and 14, here is a good guide on how to proceed.
https://www.zeusbtc.com/manuals/Antminer-S9-Hash-Board-Repair-Guide.asp