Same problem here, not with the app but the chrome extension (Mac OSX 10.15.2, Chromium Version 79.0.3945.79). Switching from MacBook Pro (2016, Retina in 1440px setting) to an external monitor (Philips, 5120 x 1440) doubles the content size. This is pretty annoying. Running the monitor while having the MacBook Pro closed is not possible.
Example Image
Wenn I open both screens and move the browser window back to the laptop it works, even when then moving it back to the monitor. After that I can close the the laptop and everything is fine.
