Recently, I replaced the trigger on my MAK-90 with a Tapco G2 double hook trigger so that I could get some US made compliance parts to replace the thumbhole stock.  Anyhow, every now and again when the trigger group isn't lubricated (i.e. bone dry), the disconnector will grab the hammer, and not let it go forward to fire another round.  It has only happened twice, but, it makes me question the reliability of my MAK-90 if my lubricant dries out.  I never had this problem with the original Chinese FCG.

Did I do something wrong OR do I need to let a few hundred rounds rip to smooth out the FCG assembly?  I also considered trying to get one more loop of the hammer spring to make sure it is extra tight, but I don't want to risk breaking anything.  Finally, I just make sure the FCG is lightly lubed before heading out and I do not have this problem.

Did you make sure that both legs of the spring are hung on the back end of the trigger?  Had the same problem with resetting and that was what it was, one of the spring legs not on all the way.

The legs appear to be hung properly.  The only issue I noticed in assembley of the new FCG was that the spring sometimes slips off on one side.  Very hard to make it happen, but, I could make it happen at once upon a time.

maybe try polishing that area? or getting a replacement spring