Incompatible front derailleur/crankset? I recently bought a Tandem from the 90's and now trying to adjust the derailleurs. But, no matter what I do, I don't manage to properly set up the 3-way front derailleur. It either


properly shifts from lowest to 2nd or
properly shifts from 2nd to highest. 


I noticed that the crank and chainwheels don't seem to fit to the rest. The front/rear rear-derailleur and the captain crankset are a black and Shimano Deore LX FC-M563 to my best guess, while the stroker crankset is silver and some "Shimano" which I cannot further specify. 

I am therefore wondering if that could be the reason for the derailleur not working properly. Or should one-shimano-fit-all, no matter which model?

I also noticed that the chainwheels seem to be not equally spaced. It's ~8mm from lowest to 2nd and ~5mm from 2nd to highest. As far as I can tell, on all my other bikes the spacing is equal and ~5mm. 
Are there such 'weird' cranksets or has it just been incorrectly assembled? i.e. could I possibly fix my problem by exchanging some spacers instead of buying a new crankset?
First of all, IMHO, when you buy an old bike you should always change inner and outer cables (cable housing) for the brakes and shifters. This will ensure that the cables have low friction and won't get stuck somewhere

Then this part "It's ~8mm from lowest to 2nd and ~5mm from 2nd to highest" makes me think that someone got the order wrong. I think the highest and the middle sprocket are on the wrong side or the crank(outer side). Or the smallest sprocket has spacers that shouldn't be there. Or maybe the middle one is lacking spacers.

99/100 Sprockets are equally spaced, because that's the way the shifter handle pulls.

Lastly, check the "front" dereaullier alingment. It should be parallel to the sprockets.