Unfortunately, many factors may cause outputs to be out of sync so it's always hard to know where the actual problem is. It could come from using different brands of equipment, cable length and quality, adapters, chipsets, video processors, LED panels, etc...
Luckily you can easily adjust your outputs in Resolume to re-synchronize everything by using the built-in delay feature in the advanced output:
Each screen can have a delay between 0 and 100 ms, to account for small delays introduced by the
signal chain after the outputs leave Resolume.
at 60 FPS, 100 ms will allow you to adjust for up to 6 frames. You would need to identify the output that's the most delayed and adjust the other ones back to match it.