That’s a nice shot Gerald and from the onboard video you can work out the exact timing of it (fairly early in the flight, with no FC enabled). I was flying it rather aggressively at the time just trying to keep it airborne (with all the trims out of whack)
Like you I was initially worried about the rather small CF wing rod and thought seriously of replacing it during construction but after a fair bit of research on the build site I decided to build it as designed & see what happens.
As the designer states it is NOT for aerobatics or any form of aggressive flying but for Long Range FPV/aerial photography so the construction is light weight & very flexible (not unlike a glider).
The majority of wing flex comments online are from people trying to fly it like a stunt plane, those using it as intended either don’t mention it or just in passing. I guess only time will tell.
The amount of flex shown in your pic is similar to what I got out of the original smaller Fox glider before I learnt how to fly it less aggressively. As we all know since Chris took ownership, it has been flown far harder than I ever did and the wing flex issue never comes up.