Wago's fail all the time, as do wire nuts. Both need to be applied properly. Applying a Wago properly is easier than applying a wire nut properly.

But Wago's really do have higher contact resistance, can have higher temps and I've personally seen more than one case of a molten Wago, including one where the whole metal part had molten its way out of the container, as well as one where the tabs had gone missing and were all locked in the 'open' position (no idea how that came to be).

I do a lot of house renovations, have installed a whole pile of solar gear (including some pretty heavy duty inverters), and have installed a complete machine shop. You're more than welcome to question all of that but I'm not in your pay and I don't need to prove anything, my personal experience is good enough for a forum comment.