Dead pedaling?

Good morning (on the East Coast)! I'm a newbie to e-biking (and reddit!), so I'm not sure what's "normal" and I just have to adjust to, but I have an issue with what I'd call "dead pedaling". I have a Globe Haul ST that I bought in October and I use it primarily to commute (3 miles one way) twice a week.

I live in a very hilly area so my ride is rarely flat, usually big ups, big downs, and slopes. On slopes and downhills, I keep pedaling to keep the motor going to so I'll maintain speed (I'm typically riding with the motor on 3, or 4-5 when I'm carrying a kid). What I've found is that it feels like my pedaling isn't catching - I'm basically just spinning loose until I hit another uphill stretch and then the chain catches and I can feel the effort again. It's very disconcerting, but I haven't been able to explain it to my bike retailer adequately so they think everything is fine. I'm just wondering if this is a normal thing or if others have experienced this, and know what I'm doing wrong or what to fix?

(cross posted from the Globe Haul subreddit)