Eaton fuller splitter slow

I have 10 spd Eaton fuller trans that's slow to go into low range. When it's in 6th and I need to go into 5th I'll flip splitter down and it takes few seconds before I hear it click into low range.. sometimes I'll do that and it will grind hard when I'm shifting from 6th to 5th. Mechanic already replaced filter and solenoid on top of trans