28 20 wrong grade display

Meaning erratic readings 

I did a 3 and a half hour ride with climbs  and the grade was looking reasonable. I think that on my previous ride maybe the atmospheric pressure was fluctuating. Any way the grade looks ok so it is not a firmware issue like in the past.

Well known fault of the current firmware. As workaround you can install CIQ-Datafields like "sensible grade". Just fixes the datafield, not the gradient readings in the climb pro screen etc.....

is BRM grade as well fixing it?

Try it, I just installed the one I mentioned.

I did a 100+ mile ride and the 1040 showed negative gradients for about 40 miles of the first 50.  However, the number of ft climbed was going up.  I dreaded turning around and coming back because I thought all of those negative gradients would be positive gradients on the way back. NOPE!  There were 40+ miles of negative gradients on the way back as well.  I finished the ride with 5000+ feet of elevation so the ride was not full of negative gradients.  This is bad when you clearly see and feel that you are riding uphill, but the gradient is negative on the garmin cpu.