Font rendering corrupted when sub-pixel order enabled

I’ve installed xfce4 desktop while using dragonboard-410c-sdcard-developer-buster-528.img sd card image. After reboot the lightdm greeted me with corrupted (unreadable) login dialog. After logging into xfce desktop all looked fine until the font rendering was changed in “Appearance->Fonts” settings. If “Sub-pixel order” is changed from None to RGB or BGR or any other option the fonts get corrupted.

Anybody has seen it or even does have a fix for it (apart just not using sub-pixel rendering)?
Could it be low video memory size? Glxinfo shows only 10Mbytes of video memory size - what’s the way of increasing the dedicated video memory size on APQ8016E ? I’ve looked into DTS and could not find anything useful. Any ideas?