Things Every Homeowner Knows About Hiring HVAC Companies: Question about York 95% condensing furnace drain.

I have been having this issue since install unit locks out for an hour (it will run longer when not very cold 45 and above as unit then produces minimal condensate). I have found the issue, and have confirmed it. Water backs up into the blower, of course furnace then shuts down. The end results are if I disconnect the coupling (circled in red in photo) and let it drain into a bucket the furnace will run for as long as I want and operate normally. I have confirmed the there is no clog in the 3/4 inch pipping and that everything is running downhill with a level. It seems some type of airlock is occurring, would this drain need a P trap or a vent to force the water down hill? would it better to add a 3-4 inch drop and shorten the run or any other suggestions are welcome.