Hi All - I just got a variable ND filter ND2 - ND400 (1 to 9 stops?)...

Just having issues at the high end (9 stops) - no mater hwo much I slow the shutter speed (I am actually going way slower than what's showing on the scale) - the shot is coming out nearly black with a slight blue tinge. This issue does not happen at one stop lower in the filter but at the max point I just can't get to produce a well exposed shot.

Any ideas?