Definitely not an unknown characteristic!! On my 400, I have no problem selecting neutral at standstill, on my GB250, as soon as it reaches running temperature, forget it!!! Both are adjusted in the same manner, and both are running on 10w 40 mineral oil. Occasionally on the 250, I have had to kill the motor, select neutral, then re-start. Any body who can remember the original Mini's with the A series engines can tell you that when the engine was cold, the gearchange was wonderful, but deteriorated as it got hotter. One of the disadvantages of running a gearbox in engine oil instead of a nice gloopy EP80 or 90 gear oil.