OK. I think I've found the where was the problem by myself by comparing saved P3D situations: One when I manually prepare the plane for take off and another when using BA46 menu to set take off.
In the saved fxml files , in engine parameters sections the GeneratorSwitch value in my startup files (which were working well with the previous version) was set to False. In the BA46 one it is set to True.
I've started a new flight proceeding as before the update but with fixed Generatorswitch values in the startup fxml file and all is running well now.
It's strange because my startup files are created from a cold & start state but it seems that this cold & start action doesn't initialise the same P3D values than the take off config one.
Skip.