I arrived at the SuperCharger in Metz, France. It is a 2-stall portable SC.
I was the first to arrive, docked and started charging at 117 kW. All fine. I entered a local supermarket to buy some roadwarrior-food.
Within 10 minutes of leaving the car, i got an alert on my iPhone that charging was interrupted. So i walk back to the car but it was charging. Glancing at the phone i noticed a second notification telling me that charging resumed quite soon after it was interrupted.
However, it was now charging at 24kW and not 100ish as it did a minute earlier.
Then i noticed the reason. A second Tesla had arrived and started charging. I got kicked out somehow when he started charging and as i was now "number two to arrive" from the SC's perspective, i got the lower priority. When the other MS started to get "fuller", my charging speed increased accordingly.
I use SC's a lot (i drive a lot) and had other MS'ses enter the second, paired Stall many times and never got kicked off from "mine" because the second, paired stall started charging. Until now. How rude...
The result was that because i was charging much much slower, i had to wait about 40 minutes longer overall (i needed a 100% range-charge to get to the next SC).
To explain the priority thing: two Stalls form one SuperCharger. An 8-Stall SC are actually four SC's and not eight. An SC has 12 "sections" capable of delivering 10kW each which are divided over both paired Stalls when both are in use. If only one Stall of the pair is in use and the cars battery has a very low State Of Charge (SOC), it will allocate all 12 sections delivering 120kW. If a second car starts using the other paired stall, sections are "taken away" from the first stall/car and allocated to the second stall. This of course reduces the charging speed of the first car. Example: The first stall, 12 sections in use, might get reduced to 9 as 3 are decoupled and allocated to the other stall.
As soon as the first car is lowering it's charging "speed" because the battery is getting "filled" more, sections are decoupled and added to the second car's stall, increasing it's charging "speed" more and more.
That's how SC's work and that is why you see MS drivers pull into Stalls of which the paired stall is not in use whenever they get the chance. Stall-pairs are easy to spot as they are called 1A and 1B, 2A and 2B etc. etc where the "1x are the two that are paired.