I've got the same windows on my new trailer. I think there is a little re-training of the brain on opening these windows that has to happen. I have instructed all in my family to "turn the knob until resistance is then gently turn to increase pressure until the window releases from the seal". I can easily see the mechanism (which seems a bit flimsy) bending or deforming if to much pressure is applied to soon.
2015 Starcraft Travel Star 299BHU Black Pearl Edition
2011 Jayco X23J (traded in)
2009 Ford F150 FX4 SuperCrew