Ground beef

[DaveDSC]

So I’m new to this forum and am having trouble submitting an intro as it freezes so I’ll just jump right into my problem.
Crumbly burgers or soft burgers.
I work with my butcher and have been playing around with a burger mix for a while then all of a sudden we are getting soft burgers that are not holding together well.
We moved the fat content up and down but it was the same.
I’m wondering if anyone has had this experience, could it be the cow was old? Meat needed resting? Meat was frozen by distributed? Meat needed drying before grinding?
Any experiences would be appreciated