AC charge rate slowly decreases to 1kw

[Starplots]

You need to try a public Type 2 (AC) charge point. (Just to be clear - trying a DC rapid charger won't prove anything).

Agreed. If it is OK on a public AC charger then it could be a poor connection on your home charger cable or the wiring to the charger.

Poor crimps, small gauge wire or loose screw terminals would give this symptom; as the joint or wire temperature increases, so does the impedance therefore reducing the current. Common Problem with some such items from the far east/ebay

 

[TheMDawg]

Andersen A2 isn’t a cheap charger. Charges my Model 3 at a solid 7kW. Car seems to be the problem.

 

[timE]

It's an all-too common problem with the CCU that generally only seems to be fixed by replacing it (under warranty) - see this (lengthy) thread. Zappi failing to charge car to 80% (Edit update: Not a problem with Zappi. Issue with AC charging/New CCU ordered)