XWayland fullscreen video glitch

When an XWayland view is fullscreen, rapid video changes produce visual glitches / artifacts. This happens under both Weston and Sway wayland compositors.
I first discovered this behavior on firefox playing a fullscreen youtube video, but I was able to reproduce with mpv (meaning this issue is not exclusive to Firefox) with the following command:

$ mpv --vo=xv <video_file>

The result can be seen here (recorded with a camera because the screenshooter didn't capture the glitch effect):

glitch

The glitch does not happen when the view is not fullscreen, or when in a window that does not use XWayland.
My graphics card:

$ lspci -v |grep -A10 VGA

00:02.0 VGA compatible controller: Intel Corporation UHD Graphics 620 (rev 07) (prog-if 00 [VGA controller])  
	Subsystem: Lenovo UHD Graphics 620
	Flags: bus master, fast devsel, latency 0, IRQ 157
	Memory at eb000000 (64-bit, non-prefetchable) [size=16M]
	Memory at a0000000 (64-bit, prefetchable) [size=256M]
	I/O ports at e000 [size=64]
	[virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
	Capabilities: <access denied>
	Kernel driver in use: i915
	Kernel modules: i915

Please let me know if any more info is needed.
(originally reported here)