So never take a car through a car wash? that's sounds ridiculous, sure hope you're kidding. Sorry, but I've been using the exact same gas pressure washer for about 15 years, and never had tailgates/liftglass leak like this, certainly not after 1yr of ownership. It's more like fitment issues and poor installation.
And to be clear, the gasket for the liftglass is completely covered by the glass, it's not a direct spray under any circumstance.
Don't get me wrong I use a pressure washer too, however read up on it, not recommended especially on an engine. Just saying, don't complain about some leaks if a pressure washer is used, it is to be expected.