Just fitted my OG-Evkin mount today, snapped in my wahoo with a satisfying click, was solid for my short ride, took the wahoo out and this was the result
also not happy with the spacers between stem and mount they deform below 5nm. (happened with the cheap alloy ones, which have other problems)
my experience with this mount is the opposite, really positive overall. I had issues with the cheap alloy computer mount, tried 2 different ones then decided to go with this one from Og-Evkin
since the first install, no issues, but I use the garmin mount so could be a problem with the wahoo specifically. Also mine is about 2yrs old so could be they changed something on the design and is generating this issues (also the comment above mine)
to be fair, the only issue I have is with the gopro/light support, I cannot get it 100% fixed, I leave it really tight and then when I'm riding it starts to come loose. Not a big issue, with the gopro is less of an issue really, with light (heavier) it can become annoying having to adjust the angle every few minutes
my suggestion is talk with the store, show them the photos, and ask for a replacement. They can send only that part of the mount, could be a quality issue with your sample specifically, too.
just wish you good luck, from other users experience the OG-Evkin communication is far from ideal