The fix I implemented was only applied on Emoncms.org as there’s no easy solution for backwards compatibility without complex migration steps. Post discusses this here: emonHP duplicate inputs from Home Assistant - #6 by TrystanLea
What I would suggest @djh is to change your script to post the data using the fulljson option, E.g:
https://emoncms.org/input/post?node=emontx&fulljson={“power1”:100,“power2”:200,“power3”:300}