not a lot you can do about it mate,fairly normal on non enthusiast boards that dont have reinforced pci-express slots.
As long as the backplate is screwe securely & you dont keep boucing the case about it will be fine.
some people ziptie the power cables to the case above so it pulls the card level but in all fairness that puts extra stress on the boards power sockets - 6 of 1 & half a dozen of the other im afraid.