It’s the same for me, but I think it’s kind of expected over BLE.
Quote from the Dongle page on the UHK Shop:
“You want a dongle either if you intend to use your UHK 80 wirelessly with some of your hosts that don’t support BLE or if the responsiveness of BLE doesn’t satisfy you. BLE works great, but mouse movement is noticeably more responsive and smoother via the dongle.”
Using the UHK Dongle is MUCH smoother.