@JonnyG: Which wireless charger do you have? Have you tried heading to Settings > Device Care > Battery > Charging, to see if Fast Wireless Charging is enabled?
I'm not familiar with the Ventev charger, but I can see that it is supposed to support 10W Fast Wireless Charging on supported Samsung phones. Please can you check the following troubleshooting steps to see if this helps at all, although please be aware that these steps are intended for Samsung wireless chargers. With this in mind, you may wish to reach out to Ventev directly to see if they're able to offer any further insight.
Im having the same issue with my S20 FE. Last night it was charging fine on my Nanami wireless charger. Tonight it keeps flitting between fast charging and normal charging. I also had a software update this morning so i think thats the issue too.
I have the same exact issue. When I place my S20 FE on my RAVPOWER 10W charger, it will fast charge for 10 seconds and then it will revert back to slow charging. I double checked with my Galaxy S9 and it is NOT a charger issue. FYI I am on the September security patch and I've tried all the recommendations in this thread.
Having same issue too. Seems like a software problem.
Same issue with the same RAVPOWER charger