Have I done something wrong?
I fitted a gxp threaded bb to a 68mm shell with a spacer on either side as the instructions from sram. Installed the Apex 1 cranks and tightened. As it got tight the cranks sropped spinning freely. I tried again with just one spacer on the driveside and it seems to work fine. Spins easily with no play. Anyone else had this?

The tech docs seem to suggest to only use the spacers if you have a wide axle chainset (73mm I think?) AND 68mm bottom bracket shell. I guess yours is not a wide axle..?

How do I know if I have a wide axle?

I imagine you should be able to find the axle length online depending on what chainset you have- however if the cups tighten up into the frame without crushing the plastic tube and when you fit the cranks and they remain free then chances are you’ve chosen wisely

Sram gxp
Road bike, 68mm no spacers
Mtb 68mm spacer each side.

Apex is road so no spacers on your frame.

Thanks that works