Bought one for self and one for girlfriend. Girlfriend has already stopped using hers because it's so unreliable -- she often has to lift her phone (Galaxy S10+) off and put it back down multiple times before it begins charging, sometimes taking a full minute to make it work.
Several times I (Pixel 4XL) have placed my phone on it to charge, only to come back 30 mins later and realise it hasn't been charging.