Hi Alain,
manual says „keytrigger by default“. So I misunderstood it is default before sync gets into count (you can read it both ways). For the described problem it does not matter so much if keytrigger is activated on sync on or not on sync on. What counts, is, that there is a keytrigger mode option. Keytrigger with sync on just makes this little difference you can only change the LFO speed divided or multipled relatively to the master tempo.
Anyway, still there is the exceptional issue with the random LFO wave. All other LFO waveforms (sine, saw, rev saw, square) are starting their cycle flawlessly on keypress, regardless what tempo/note length the sync of the LFO is set to.
But when the wave is set to random, a „keytrigger“ is only in effect if the LFO tempo exactly matches (or divides) the tempo of the master arp or sequencer. Which makes it a bit hard to play well by hand because the keytriggers have to be „on time“ with the clock (you correctly meantioned this in your post, that‘s why I got zu„weird“ delays). This also means you simply can‘t play a keysynced random-LFO free on the keyboard like it‘s working so well with the other LFO waveforms.
I hope I cleared the issue a bit more.