Having the same issue… We have a 2016 HRV, never had any issues with water in the rear gate until yesterday. I went to close the hatch and heard the slosh! I live in Portland, OR and we had record rainfall the past few days that might have something to do with it. I had an issue with our sunroof leaking last year into the floor board that was an easy fix I cleaned out the drain plugs in the sunroof opening, haven’t had a problem since. The rear gate is a new one I also noticed today water building up inside the right side taillight. I will call Honda to let them know I’m having the same issue and reference this forum doubt they’ll help but doesn’t hurt to try! I’ll check out the suggestions y’all have given in this discussion and report back on what I find.