PV surplus, what's wrong

[bruma59]

working with firmxare bèta 58.1 (also with privoius versions) V3

sending the grid information from a Belgian digital meter to the pGrid of the go-e (minus grid injection, positive grid use)
only the pGrid has a value, others are 0
fst= -1350 (it doesn't matter what I put in here)
pgt= -140 (for PV surplus)
When the pGrid is lower than the pgt car starts to charge (status=12, while it is asked much lower with the fst, it's even fst independant)
Result charging start, sees too much electricity use stops and repeats it in cycles until there is enough PV surplus

power = digital meters grid use
when car is charging I send following in node-red
msg = { payload: "{pGrid:" + power +",pAkku:0, pPv:0}"};
charging works correctly around the asked pgt

To start charging correctly I have to change power with
power = (power - flow.get("fst") + flow.get("pgt")); (status=17)

The car starts to charge correctly when grid injection is low enough, and when it's charging the instant power is used again instead of the corrected formula

I've tried different paramters but didn't found my fault yet