Missing letters in Login screen and System settings

@danielt, @Loic,
Whenever I logout the session and try to login, letters are missing in the Login screen. And also, letters vanish in System settings page too.

I’m using Linaro snapshot-405, LXQT desktop and SDDM as Display Manager.

This is how the login page looks with the Breeze theme of SDDM.
I tried changing the theme of SDDM from Breeze to sugar-candy and still the problem exists.

This is the System settings page, with the disappeared letters.

What is the cause for these problems with the Display? How can this be solved?

Thanks in advance…!

Any update @danielt @Loic on this issue?

Thanks in advance…!