Icarus can run the lfos in polyphonic (per voice) and monophonic (global for all voices) modes. The mono button defines this. Per default the lfos and the arp run in softsync mode. If you activate mono the lfo will only retrigger when no voices have been playing before. Otherwise it works like a freerunning lfo.
When i did sounddesign i usually used 'softsync with mono' for filtersweeps. It is a hybrid mode which combines the advantages of a retriggered lfo and a freerunning lfo. Here you achive similar results like with a free running lfo, however with the advantage, that you can define with phase where the lfo starts playing when you press the first key on the keyboard.
This way you can also make a voices sync with the wavetable position. I used this kind of setup in many vocoder patches.
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I checked it out and it worked as expected (at least here). Maybe you didn't set key tracking and fade to to 0.
Setting an Lfo for free running:
1) Setup ->Arp/Lfo Free
2) In the Lfo: Mono, no Env, key to 0, fadein to 0
For this purpose there are also 16 additional Lfos in the matrix. They are always free running, no matter what settings you do in setup. Select 'Sine X Hz' as matrix source.