Phone only works or charges with rear cover removed. Possible causes?

I replaced the LCD, battery and rear cover on this phone. I tested it before attaching the new rear cover, the screen worked, and the phone went through a charge and discharge cycle as normal. Then I replaced the rear cover and left it to sit under some slight pressure while the adhesive set overnight.

Next day the screen won't come on, and there's no indicator lights when I plug it into a charger. My USB ammeter shows it drawing only 0.17A -same as I've seen when this phone crashes or shuts down after a boot loop.

Has anyone observed this behavior before? What could cause the phone to work only when no rear cover is attached?