Hy Tim,
I have found a hardware hack that solved this issue of only 1 fan being detected:
First, find out wich fan conector is the one that does not see the actual fan, then move the conector, 2 resistors and 3 capacitors to an unpopulated fan plug.
Are you good with soldering, or maybe you have a friend that can do SMD soldering? (Difficulty level=low, I managed this with only a soldering iron- but crappy job, oh well, it works...)

https://drive.google.com/folderview?id=1klSzNzI1Z7DLqtzd1NGQxUKRSR2RB_mo

Notice that I moved the fan conector from Fan 5 (this was not detecting the fan in my case) to Fan 4, also R145, R147, C192,C194 and C195 to their respective counterparts for Fan 4.

When measuring with a multimeter, R145 showed only a few ohms (should have measured in Kohm range). The actual smd components were not defect, but something else in the controller was defect.
Also, you cannot move the plug to any unpopulated plugs on the board, because I also had to measure to see ifMihailnpopulated plug was defect. (Probably it had the same conection to the controller). In my case the Fan 3 plug also showed 0 ohms for R141.
Measure first!

Now the controller works as expected.


BUT,  I still want to learn to compile bmminer succesfully. Because I am curious...
Any help would be apreciated, I am an electronics hobbyist  advanced level, but a noob in compiling/crosscompiling.

Regards,
Mihail