On the sticking in gear, My WD -45 did this and in time i did these things to my tractor and it helped. - The key slot on the shifter lever was worn, i built it up and made it fit key correct. - I put a new key in the housing just under the snap ring, it has a pin from the side you punch out and put a new one in, it will fit the shifter's slot. - I am not sure if this helps but i dump in a quart of luscs oil additive every now and then.
If i can better describe this, please ask because it helped my tractor from sticking in a gear. Basicly the play in the lever and key gave it play to pop out.