I'm trying to install a brand new SHIMANO Deore FC-M590-L Hollowtech II crankset. I measured my bb shell to 68 mm and my old bb was also a 68 mm. The new bottom bracket is designed for 68-73 shells so I have to use spacers. As far as I can tell from instructions I have to use the three 2.5 mm spacers given in the package. Two on right and one on left side.

Problem is that left crank arm seemingly won't go all the way in. I'd say there's 1-2 mm of splines on left arm that is unattached to splines of the spindle. There is no room to push arms further in on either side. I must have hit this thing with a rubber maul like 50 times. I even broke the tip of the safety plate. Still won't go all the way in. Consequently when I try to finger-tighten the preload as much as possible there is still a couple mm of play on left arm. There is no play on right arm. What could be causing this? Should I remove the single spacer on left side?