Ok, good news. Apparently upgrading from El Capitan 10.11.6 to Sierra 10.12.2 it no longer corrupts my recordings with hiss´, pops, and screeches every 10-20 seconds while recording into logic or reaper (making it impossible to work with).
I do not know if this will help everybody and I wish the best of luck.
Maybe the FW 1.90 was written for OSX Sierra. One can only guess.
Ps, remember to backup all your stuff before upgrading!
