Finally got to try the dt400 on the road but trying to wheel out of the garage it felt like brake binding, backed the brake off to non existent, still tight, backed the spindle nut and ok, tighten up and cannot spin the wheel. Have to take it off tomorrow and look. Any pointers as to what could be the problem?

That acts like the correct spacers aren't in place. Look at an exploded view in the manual and make sure yours are all there. With correct spacers the axle nut tightens against them and not part of the rotating assembly.

Especially the spacer inside the hub between the bearings...

I put some larger tires on my Dt3 and it would grab trying to back up. Turned out the chain. Guard was grabbing the big knobbies on the Pirellis. Bent guard in and all was good.

May need to bend the rear wheel hub attach strut or brake actuation rod, either could be rubbing the tire, or chain guard. If it's worse in reverse it's probably the sprocket catching the chain from wear.

Have you checked your brakes? I was having trouble with my back wheel spinning on my DT 360 after I first purchased it. I took the wheel off and the brake pads had become delaminated from the brake shoes. The pads were floating around and probable got caught in an area that created the resistance.

soon as I pulled the wheel I could see the problem, spacer/bush on the brake plate was inserted from the wrong side, lucky I hadn't put any grease through the nipple........is it a special grease gun? mine will not locate on the nipples, hitting thr
the backplate.