Could you try knight walker kernel and then check it again?I think I found the problem after several tests, the CHARGER_TEMP_MAX is a little low.
With a ACC magisk module in Termux, find that the charging speed is related to that CHARGER_TEMP and not the battery temperature.
With 840 it charges at 6 watts (1200mA), (cold smartphone at 24°C rainy weather).
With 906 it charges at 2 watts (400mA), (hot smartphone at 41°C ambient temperature).
View attachment 5468783
To view the CHARGER_TEMP and CHARGER_TEMP_MAX in Termux
I cooled my smartphone and it charged normally, and the speed was in relation to CHARGER_TEMP. The ambient temperature where I live is 41°C. (maybe that's why not the same speed as yours)
View attachment 5468785