Same here
SolydK 64bit [Debian KDE] on VBox VM Windows 7 host
Opera 51.0.2830.34
link to screen capture at ibb.co
includes both monitors [left=guest Opera right=host Win7]
https://image.ibb.co/jDk40n/full_desktop_opera_linux_fail.jpg
BTW I had to set SolydK for 84DPI as standard linux 72 is too small and new Debian/KDE 96 [matches windows] is too large on everything.
Yep, just keep working on things until you break them so you can come back and "save the world" [meant for Debian as many more things are borked can't change date format for Mon 19 Feb 18 only choice 02/19/2018 or Monday February 19, 2018]
Thanks for getting next release fixed and "respecting" OS font settings.