cog flickering and not HW accelerated on NXP iMX8M-Plus

[escherstair]

I have a SoM from Toradex, with NXP iMX8M-Plus. The OS is TorizonOS (based on kernel 5.15.52) with some pre-built containers

SoC is: 'i.MX8MP'
SoC has GPU: true
SoC has DPU: false
g2d implementation: viv
Removing previously created '.X*-lock' entries under /tmp before starting Weston. Pass 'IGNORE_X_LOCKS=1' environment variable to Weston container to disable this behavior.
dos2unix: converting file /etc/xdg/weston/weston.ini to Unix format...
dos2unix: converting file /etc/xdg/weston-dev/weston.ini to Unix format...
00:00:00.000 [INFO] [seatd/seat.c:39] Created VT-bound seat seat0
00:00:00.000 [INFO] [seatd/seatd.c:194] seatd started
Date: 2024-03-05 UTC
[09:40:19.211] weston 10.0.1
               https://wayland.freedesktop.org
               Bug reports to: https://gitlab.freedesktop.org/wayland/weston/issues/
               Build: lf-5.15.52-2.1.0-10-g9452feba
[09:40:19.211] Command line: weston -Bdrm-backend.so --current-mode -Swayland-0
[09:40:19.211] OS: Linux, 5.15.129-6.6.0-devel+git.756e3199ba82, #1-TorizonCore SMP PREEMPT Fri Feb 23 14:24:18 UTC 2024, aarch64

The containers are: torizon/cog:3.2.0 and torizon/weston-vivante:3.3.0 I use

torizon@649aeaf0fbbc:/$ cog --version
0.16.1 (WPE WebKit 2.38.6)

and I browse to https://webglsamples.org/fishtank/fishtank.html whith 1 fish and no sharks. I see that cog is flickering, and sometimes big white squares are shown over the webpage. Moreover the performace are poor (14 FPS) and I suspect the HW acceleration is not in use (NXP told me that I should see 60 FPS on the fishtank example). Here iks the log from cog```

(cog:1): GLib-GIO-WARNING **: 09:40:20.217: Your application does not implement g_application_activate() and has no handlers connected to the 'activate' signal. It should do one of these. Cog-Core-Message: 09:40:20.452: https://webglsamples.org/fishtank/fishtank.html Load started. Cog-Core-Message: 09:40:21.007: https://webglsamples.org/fishtank/fishtank.html Loading... Cog-Core-Message: 09:40:21.701: https://webglsamples.org/fishtank/fishtank.html Loaded successfully.

Should I specify some command line parameter to cog?