Anyways I find that some of my aircraft since I got GSX start to lose all power half way through loading, does anyone have this issue and know how to fix it?
That's not obviously "caused" by GSX, it's the fact that you must turn off your engines while loading and, if your airplane doesn't have an alternate source of power, you are draining the battery.
Most of the advanced 3rd party airplanes, like the ones from PMDG, Aerosoft, Wilco, etc, have they own power sources that you can use, such as GPUs or External power simulations, so you must activate them as soon as you turn off your engines.
For default airplanes, you will probably need to use FSUIPC, which has an option to prevent the battery to be drained.
