Display does update properly when resizing manually though.
I've recorded a video in order to understand the issue easily:
https://www.youtube.com/watch?v=Eh1DEtKflbQ
I don't know if it's relevant, but this error appears in the log when toggling off:
E: buffer.cpp:157: FlushSocket failed
OS: Debian GNU/Linux buster/sid x86_64
Kernel: 4.19.0-4-amd64
WM: i3
CPU: Intel i7-6700HQ (8) @ 3.500GHz
GPU: NVIDIA GeForce GTX 960M
PPSSPP: v1.8.0-102-g057e720b2