I think next trip to the gym, leave off the device at first and set up like you're giving your partner a hip belay See what happens...
I shamefully admit, I am a palm-upper, although I now attempt to change it up with palms down. Not about strength, I'm weak . Learned to belay with a hip belay 30 years ago. Transfered the habit to a sticht-plate, then to a figure 8, to a Lowe Tuber, and so on. I have never dropped or screwed up a belay in 30 years. I have a scar on my back catching a fall with a hip belay. I will still give an occ. hip belay to a second following me.
However, adapt to your environment. When in the gym, do as the gymmies do.