I'm not sure why latency would be different on different channels, but soft synth recording is not compensated for audio latency like recording from a hardware inputs. You can try lowering your buffer to minimize the latency, but it would be better to just freeze/bounce the audio rather than using synth recording. Synth recording is only necessary when you want to capture a live performance while tweaking synth parameters that can't be easily automated.
- If you're rendering audio from existing MIDI you should just freeze the synth.
- If recording while performing live on a controller, record the MIDI track, and then freeze the synth.
- If you're recording audio from a pattern being played internally, drag that pattern out of SD2 into the MIDI track and freeze the synth.