Engine Re-Assy Problem

I assume you have had the pistons out of the motor ? maybe the ones that locked are as mentioned above installed the wrong way. Check the position of the oiling hole on the rods for the pistons in question. The oiling hole should be pointing towards the opposite cylinder on the rod journal. My guess is that - or the crank was improperly sized for the bearings or the big end of the rods were not resized and are ovaled.