A quick/fast/unauthorized way to get chain off crossover: Use a thin bladed screwdriver at chain/chainring junction. Pedal backwards. Chain pops off. Align both cranks where you want them. Re-install chain same way, but have someone hold up back end of tandem and move pedal forward and chain gets seated.
Or, loosen eccentric, etc.
However we on purpose have our cross over chain set up with pedals 90 degrees out of phase. Reason: there is always a power stroke going 'over the top.' Easier climbing (for us). Quicker get-away from lights. Stoker stays seated at stops and provides instant over the top power as we push off. Also, less tandem sway when stomping on the pedals as we do not both push hard with left foot then both with right foot, but we alternate that motion by being 90 degrees out of phase.
Yes some people say we are 'goofy footed' but been doing it successfully for over 29 years.
Pedal on TWOgether!
Rudy and Kay/Zona tandem