I've found render bug on a multiple RK3288 devices with Mali-T760 GPUs. The devices are on driver versions 11 and 14, but both have the same problem. Here is the version string for one of the devices: OpenGL ES 3.2 v1.r11p0-00rel0
The problem appears when mapping buffers to uniforms and calling glFlush multiple times per frame. I have a simple Android project that reproduces the problem here. The image below on the left is the output on my Mali devices, the image on the right is what you see when you remove the glFlush command or run the original code on a different device such as a Pixel 1.
Thanks for the bug report; I'll follow up with the driver team. The drivers you have are relatively old (our latest release for Mali-T760 is r26), so it is possible that this has already been fixed but I'll see if we can find a workaround for you.
Thanks Pete. If it is fixed now it would be useful to know what version it was fixed in so I can ask my OEM about an update and narrow down any workarounds in user code to that version.