I have a mac with high sierra too and can't get my kb37 to work at all even after following every instruction on multiple forums.
If I don't get a solution soon, I'm selling the kb37 and going back to my boss eight track recorder......no issues, no latency and no trouble for 12 years.
Computers have to be the most unreliable, unpredictable pieces of crap out there!
Anyway, I hope we both find a solution soon....so frustrating!