Series 2 Jumping out of low range

Hi guys
Whilst enjoying being out in the snow today in the 2a i noticed it was jumping out of low on the over run now other than testing it all after swapping the HRTC to a std transfer box i've never used low range and never had this on my previous series landys, so can anyone tell me what it mite please

When you fitted the standard transfer box did you rebuild it and if so did you put grease on the shims that set preload on shaft thinking grease in hole that selector rod slides into.
Take the detent ball and spring out and look down hole to check if detent slot showing on shaft.
Is the red lever sitting in normal position inside cab some folks refit the lower lever mount on the wrong side of the casing.

I'm pretty sure we used grease on the shafts and yes the lever is in the right place as i made that same mistake putting the lever back on so had to refit it, will look into the detent spring and ball