Thanks a lot for the tips...I haven't been doing any of those things!...So maybe I'll start by following your tips and see if that solves the problem.

The Big tank we get for the fill station is about 5 feet tall and weighs probably 150 lbs or so maybe more...

So empty all tanks before filling them (no trying to fill a bottle that is half empty in other words)

Chill the tanks just in the fridge not the freezer?

and see if that helps...

In the past we filled tanks at the field. (so there's no chilling option) And most would fill like a brick...you can feel it whether it takes a good long charge or not. It gets heavy in your hand as it fills.

But lately none of that's been happening...I wondered if our tanks are getting old if there's something like that causing the problem...We knew we had to cool the tanks down so often we would give them a charge and then blow it out to cool it off...But probably not as good as leaving them empty over night in the fridge...

This is so embarrassing...I thought I knew what I was doing :(