Just received a mid-production BNSF SD40-2 and have been running it around the layout just long enough to realize the knuckle couplers on this unit seem different than other Kato diesels I own. The couplers stay attached well, but getting them to couple up to another diesel or car is the problem. Is this a "new" coupler design from Kato? I tried hooking up a Kato AC4400 to this unit which took some doing. The knuckle coupler of the SD40-2 just wouldn't stay attached to the knuckle coupler of the AC4400 unless some side pressure was applied to the SD unit's frame - sort of twisting the engine just slightly while it was still on the rails. Only then would it grab and hold on to the AC4400's coupler. And when finally hooked up with the AC4400, if they didn't start to move at the exact same moment, they'd decouple immediately and need recoupled by hand again. Once they were coupled and started together as a unit - they stayed coupled up traversing the layout. But these couplers on the SD40-2 seem quite different than the Kato couplers I have on other units. Has anyone else experienced this? I read that these couplers are Kato's "semi-automatic" coupler design...is that the same coupler that they've installed on other diesels within the last few years?