Interesting that the solution that was accepted fixed the OP’s issue, which seems to be a different issue than others were reporting later on in the thread.
OP’s issue was that of page zoom, thus CTRL + - / CTRL + + fixed it. (CTRL + 0 wasn’t mentioned, but will restore the page to 100% if accidental zooming should ever happen.)
Other posters’ issues seemed to be related to losing scrollbars due to the window being sized beyond the monitor’s viewport when going into full-screen mode. (In fact, it almost seems like that’s the problem: full screen sizing of the app doesn’t subtract the width/height of scrollbars, as that is exactly the distance that it extends beyond the viewport.) Unfortunately, the CTRL + - / CTRL + + / CTRL + 0 fix for OP’s issue does not resolve this one.
Will await a resolution per @Mandy_Sponholtz 's ticket and will continue to follow this particular issue’s thread.