So the good news is: Atfer 2y with xert today I finally cracked the 300w TP
Whats weird is that in the activity view and also the rendered strava BT picture it claims +89w for TP. Looking at the progression graph above, which shows the correct increase, its rather +11w.
One thing to mention is that just before todays BT ride I switched from no decay to optimal decay, so maybe that plays in it? But 78w TP decay within few hours would probably also not be intended I guess.