Application freezes at startup when two QQuickViews are used in Weston

On embedded Linux system having i.MX8 SoC, Weston compositor and Qt 5.12.8, the attached application freezes either directly at the startup or then after timer has triggered twice.
if environment variable "QSG_RENDER_LOOP=basic" is set, the application either freezes from the start or runs until it exits from the timer expiry at 60 seconds.
The stacktrace from freeze (with basic render loop) has been attached.

Further analysis has shown that the freeze happens in qwaylandglcontext.cpp, where a call to

eglSwapBuffers(m_eglDisplay, eglSurface);

never returns.

if mSupportNonBlockingSwap is forced to false in the constructor in the same file, the issue does not occur. The check that is supposed to set mSupportNonBlockingSwap to false reads both attributes successfully and gets value 0 for EGL_MIN_SWAP_INTERVAL, leaving the mSupportNonBlockingSwap as true, as it should.

About environment:
At least Qt 5.12.4 is required.

This issue has been witnessed on:
Weston 6.0.1
Kernel 4.19.35
Vivante EGL driver: 6.4.0
Qt 5.12.8

The setup can be achieved with this Yocto manifest:
https://source.codeaurora.org/external/imx/imx-manifest/tree/imx-4.19.35-1.1.0.xml?h=imx-linux-warrior
(external/imx/imx-manifest revision 65f98c7dda141e8a6812b414916113bca1e571ef)
and upgrading the meta-qt5 to revision 7d0b17aa229edc9e138edfe0e8477fbbe9013ba6 (Qt 5.12.8).
HW used for testing: NXP MCIMX8M-EVK: Evaluation Kit for the i.MX 8M Applications Processor (i.MX8M Quad), "device" for build is imx8mqevk

This issue could not be reproduced on:
Weston 4.0.0
Kernel 4.14.78
Vivante EGL driver 6.2.4
Qt 5.12.8