Poly Sequencing Layer A and B vs Output A and B

[musicmaker]

Default Programs U1 P123 for example  (P114 is similar)
Connect only audio outputs to output B (L+R)
Turn OFF any modulation (LFO's, ModMatrix) destinations.

Turn on split A/B, turn off layer B
start sequencer
No sound  (A is active only)
Turn on layer B
Low volume notes on B-Left, high volume on-Right (not always the same notes)

Disable stack/split
Select Layer A only (turn off  Layer B)
Start Sequencer
Some notes are played on Output A left channel, some not. Not always the same notes. B L/R no sound
Select Layer B (only)
Start Sequencer
Low volume notes played on left channel B,and high volume on right channel B (not alway the same notes)

The high and low output volume changes by note does not occur in Multi-mode. (in this situation  B Left is low volume, Right is high)

What is setting the volume for B left and Right here by note ?
How do Layer A only, Layer B only, Split and Stack affect A and B outputs in Multi and non-Multi mode ?
Can't get my head around this one
REV2/16 Desktop 1.1.0.3

[musicmaker]

It much easier to reproduce, like this:
Use headphones on the REV2
Use Audio L/R on  output B only
Select U3 P33 (default program) (there are several other presets, but not all that expose this issue.
Select Edit Layer B  (Split and Stack turned off)
Start sequencer or play notes via MIDI
The audio switches from headphone to Output B back and forth.
On some other patches Output B sounds different when the headphone sound is there or not.
It seems a bit this has to do with the BPM but can't find the reason why.
REV2/16 Desktop
1.1.0.3
Anyone else has the same result ? Bug or defect REV2 ... (?)