After waking up my laptop (running Ubuntu 16.04 LTS) from suspension, the displayed screen resolution was suddenly much lower (factor of 2 or more?). Checking the set solution (both xrandr and in the system settings), it still displays the old default resolution. The only change since the last reboot was an update of the kernel which I reverted. In addition, I booted an older kernel version, i.e. my system should be in the state of an earlier reboot before the update, but the resolution problem persists. Adding a new mode to xrandr with a higher resolution failed due to a "BadMatch", presumably because such high resolution is not supported by the screen.
Tips and possible solutions welcome!