Already not for the first time I notice that GUR2 readjusts its X zero position
As a result the coherence between GUR1X and GUR2X is lost, but between GUR2X and GUR2Y shows up. It seems that these two signals mix at some point.
Can you go back in time before the X-position jumped to plot the x1-x2 and x2-y2 coherences? Just to see what things look like?
DAQ is not working now but ordinary the coherence between GUR1X and GUR2X is ~1 at 0.1 - 10 Hz and between GUR2X and GUR2Y is ~0.