Have the same problem and with a replaced HV battery pack with less a year. In Portugal there are 20 or more 85 owners that got the same problem and it gets worse over 80% (we need more than 80% SoC due to extremely bad public network).
Clearly there is an issue here! Why?! Nobody from Tesla tells it. To me they told it was firmware, like the TOCWA here in Portugal we made the same test and we got the same result. There is a decrease in 20-30% in Supercharging speed session and also in CHAdeMO charging which is surprising
Tesla needs to clear out this as most of us are getting a dramatic change in cars features.