Ok, finally found it what was the problem.

Octatrack manual - page 131

When in RECORDING SETUP 1 menu, recorder trig’s [TRIG] shows the sampling sources. Activated sources are indicated by inverted graphics. De-/Activate recording source by pressing [TRIG]+[AB]/[CD]/[MIDI].

I wasn’t sampling the SRC3 source at all even SRC3 was selected MAIN (it was deactivated).

Learned

  • Track recorder sampling