I am on my 4th frame this year! Not impressed with the fragility of these, so FWIW I just added one of these:
I just found this on AliExpress: | For BetaFPV Meteor75 Pro Carbon Fiber Chassis Motor Installation Plate Strengthen Lightweight Bottom Board Drone Frame Part
Does make the frame significantly stiffer, early days but it has taken a few big hits and frame has survived so far. 