Hi Kringel,
we think we understand the problem.
Are you specifying the algo in the command line? --par=150,5 ?
It is entering the wrong algo in the new version.
In t3 version it was working because we used to ignore the par argument while mining Beam (because of the last fork, a verification that was never removed). We have been preparing for the next algo change and we took it out.
You need to write --par=150,5,3 or do not use par at all, miniZ will enter the right algo if it is not specified.

Hope this helps.
Cheers
I've checked this, the Nicehash client fork indeed specifies --par=150,5 in the command line. All I could do for now is adding --par=150,5,3 in addition to --par=150,5 (before it, actually); that didn't help. I'll contact the author of the program.