Re: Powersoft powerlimiting, and GFI's. Is the power limiting tripping the GFI?
Ok I'm in the UK but I use both D/Q series and K series Powersofts and like Bennett I doubt it's the amps, GFI or RCDs as we call them do get more sensitive or more prone to errors if they are dropped or regularly tripped, either test it or replace it first.
My worst experience was in a local hall here where we had all the backline and video kit off of one GFI and the cumulative earth leak of several valve amps older keyboards video kit etc tripped the thing, no one device showed any fault but we solved it by splitting the gear over 2 GFIs on the same phase and ta da no more trips. I suspect you had a similar situation cumulative build up of stray current and an over sensitive GFI.
Edit: When I re read your post are you sure your mains cable hasn't got a bad neutral or be internally damaged that could cause a voltage difference at higher currents and possibly take out the GFI G
