Well, Wago connectors have been around for almost 25 years in 230V country, and I never heard of as much as a single issue - on the contrary, most electricians in Europe are praising them as the ideal solution preventing fires caused by loose screw connections (due to alleged copper cold flux and lazy installers). Basically they say there's a spring inside that will always keep constant pressure, no matter how much the copper wire deforms. When filled with antioxidant paste they are even listed for aluminum wire and Al-Cu splices in Germany.
For devices, VDE had a hard time allowing push-ins for anything but light switches (max. 10A) but eventually in the early 90s they were allowed for receptacles (16A) and now it is flat out impossible to buy receptacles with screw terminals anywhere in Continental Europe and has been for the past 15 years. I've yet had to see a melted one, even under continuous high load (mind you, you can circuits up to 100% here). Then, I've seen plenty of loose screws.
I long resisted Wago connectors for splicing, but they are so much easier and faster to use that I finally resigned and considered them time-tested enough after 20 years.
