Are you trying to hear it using one oscillator or two, Yorgos? Try dialing up two saw waves, same pitch, no detune, no sync, no slop, slow amp attack, filter open... If you play and hold a single note, the two oscillators are clearly exactly in tune with each other. Then while you're still sustaining the note, turn the slop setting all the way to '5'... If you can't hear the random beating of the oscillators drifting in and out of tune with each other, I don't know what to say. It's working on my Tempest, and indeed always has.
does the slop feature on your tempest work similar to below?
https://www.youtube.com/watch?v=Qh4YDAFJ1FQ&t=265that's what i would expect oscillator slop to mean, basically a lax of control over the exact pitch of the oscillators. however, what i get sounds like a phase drift (and yes, sync is turned off).
here is a demonstation:
http://picosong.com/t7u4/this is an initialized patch with a saw for osc 1 and 2. in the first ten seconds i turn slop all the way to 5. after 0:10 i begin mixing in osc 2 with slop turned off again. at 0:19 i sustain a note and begin turning slop up. as you said, i do notice a drift when comparing the osc side by side. but this is not a tuning drift, but what sounds like phasing.
at 0:35 i tweak the patch to something i might use in a real situation and play some chords. the 50/50 mix with a slop of 5 does create a nice unison effect which you hear at 0:50, but not the slop functionality of other sequential/dsi synths.
if you listen on, at 1:15 i mimic slop by using lfo 1, random waveform routed to osc1 pitch. i have lfo 1's freq at 0, and amount varying from 1-8. an amount of 1 introduces a drift of about 10 cents according to ableton's tuner. with note reset on, i feel this is a close emulation of slop, but any higher than a slop of 2 becomes very detuned. it would be nice to have a more gradual control of cent variance.