definitely not on purpose. A free running mixer #1 makes the randomization ... different - unless the reflex unit has been reset/bypassed to make mixer #1 irrelevant.
the mixer latch arms on the pacific pinball museum's Yacht Club that I gutted a few weeks ago are in good shape. PM me your mailing address and I'll send them to ya. If you want to donate something to the PPM, you can do that on their web site.
if your mixer 4 arm is ok (roller not wobbling on worn shaft), I'll just send ya 3 arms.