Sony SEL2470GM LENS not focusing when zoomed

[Cadam54]

I have a Sony 24-70 GM that does not focus when I zoom in past 24mm. At 24mm however it works perfectly fine. 
the autofocusing ring works at 24mm as well but when zoomed in does not work. Ive tried two different camera bodies and its the same issue. I have boiled it down to it being some sort of mechanical issue which is hard to believe considering the issue started in the studio and not in the field, Ive never dropped it and have taken very good care. Has anyone had this issue and is there any advice someone can offer before I spend a small fortune on sending it in for repair?

[Cadam54]

Update: It does auto-focus and manual focus at close ranges when zoomed but won't focus at a distance.