This is a really specific bug with either Zebra2 or Renoise, and once again, no biggie.
With the basic single oscillator sound that’s loaded on Zebra’s initialisation, set the arpeggiator to 1/64 with the 1st note at transpose 0, and 2nd note with transpose +12, and a step number of 2. Then in global/fx, set voices to arpeggiator.
Then set 2 different notes to play together at the start of a pattern.
Play it back several times, and you’ll hopefully notice that it sometimes sounds different.
If I put a D1 (delay) command on the 2nd note, it seems to play back correctly and consistently.
This has something to do with the octave setting in zebra 's arp.
Change arp speed to 1/16 and octave setting to 2 and you’ll notice that the beginning of the pattern is always a bit different .( like your example but slower because of thearp speed )
To change the problem just don’t put two notes on the same line …I guess this has something to do with zebra’s voice allocation
please report this to the Zebra devs. Its very very unlikely that this is a problem in Renoise, but more likely that theres something wrong in the plugin. Even if we have to fix/add something for this, only the plugin devs can bring in some light here, tell us / why / what happens exactly here…