Workbench kow colors and low resolution on Pimiga 5

May someone provide advice on a weird issue with Pimiga 5? I hooked it up to an old HDMI TV with 1680x1050 resolution. When the A1200 Workbench appears, it appears low resolution (with screen cropping) and low colors (about four colors). But when I press [F12] for the Piberry GUI, it shows fine. Also, when I exit Pimiga, the Raspberry Pi OS desktop shows fine.

When I view the list of screen modes, they work when I click the Test button. But when I click the Use button, I get the message “Intuition is attempting to reset the Workbench screen. Please close all windows, except Drawers”. I closed the stats window and the dock, but still get this message when I click Retry.

I then selected the first resolution in the list, clicked Test, looked fine, then clicked Save. When I reset the Amiga via Piberry, it showed a black screen. When I rebooted Pimiga (the entire Raspberry Pi), it only shows the pre-Workbench splash screen, then stops.

Any ideas why Workbench isn’t displaying properly? I tried messing around with random settings in Piberry’s Display section, but no help. Thanks!