eepcsum doesn't really work like that in Sherwood. It's a bit different from Mullion.
You can't exactly fix it just like that. eepcsum will not tell you what address is broken or not. Only the calculated value that "should be" yes. Which is only half of the puzzle.
The address needs to be found by other means and then compare its value to the output of eepcsum. Address appears to be
I went over this here for example:
https://www.psx-place.com/threads/modifying-syscon-fan-settings-better-than-webman.34626
Also if he can't use SW mode with python, maybe he is using wrong old script?
He could still use the execute.exe AND debug.exe to do the same thing... If somehow he likes the utility more.
You can type whatever command you want with execute.exe while you have debug.exe open to see the outputs.
But...
In his case, he doesn't have to do anything. If his checksum were a problem, the machine would beep red immediately and not turn on at all. No response from power button.
His machine was working perfectly fine for years. Then he opened to delid or whatever, and now strange problems...
Try to disassemble again carefully and put together exactly like it was before? Maybe something is shorting due to improper assembly or something stupid like that.
Otherwise the problem could be delid damage, perhaps precarious contact under CPU, or NOR flash who knows, from flexing the board anything can happen.
But no need to overcomplicate things. It's funny to have this kind of talk here. Looks like it's unrelated but this is exactly the spirit of this whole thread hehehe.
Good luck