I've stopped buying F tickets on EK due to this. (I fly mostly J but used to occasionally treat myself to F)

I am now buying J tickets only and use miles to upgrade to F if needed . My travel is mostly for personal reasons and im fairly flexible.

Ek did involuntarily downgrade me twice in the last one year ( J tickets upgraded to F using miles ). The flights were ex DXB any way. They substituted it with a 2 class. The miles I used to upgrade were credited back in a day.