According to one of the posts, “I have 4 chargers. 1 is unofficial. 2 is official – 1 was the packaged 6p charger and the other bought from Google store. None of these work. I either get ‘Charging ‘or ‘Charging Slowly’. This never happened before Pie. I also have a battery backup that no longer fast charges my phone. The only charger that works is the charger that came with the pixel.”
It seems that a factory reset of the phone did nothing to alleviate the problems, and that this also doesn’t seem to be brand-specific as users are reporting various issues with different brands of chargers. Now for the most part the complaints seem to be by owners of the Pixel XL, meaning that the Pixel, Pixel 2, Pixel 2 XL aren’t affected (there is one complaint by a Pixel 2 XL user, but for the most part it seems to be Pixel XL users).
It is unclear if Google will be looking into this issue but if you do have a Pixel XL, maybe you might want to hold off on updating to Android 9.0 Pie if quick charging is a feature you don’t want to lose.