Soldato
I have just connected mine to the long lance as its supposed to be better for applying soaps etc.
Even when using the long lance the multi head/nozzle comes off easily, which suggests yours is indeed faulty.
Mine is definitely faulty, completely stuck solid. Pulling back on the QR collar and pulling with my entire strength it doesn't budge. Not an issue as I say because I have the Greenworks. Really happy with the Greenworks as the motor/pump isn't in the trigger gun itself like Worx, so you can change the hose and trigger to a more traditional setup.
However, the Greenworks is ridiculously expensive for what it is. Brand new the unit is .c £149 (can go down to £100 to £125 on deal) but that's without any batteries or charger - being 40V batteries they're expensive and you need min 1 x 4aH. You're looking at £250 to £300 for the unit with 1 x 4aH battery and charger, which is decent Karcher mains powered territory.