Uniform blocks can't be read on Galaxy S6(Mali-T760 MP8)

Hello

Fragment Shader can't read uniform block On Galaxy S6(Mali-T760 MP8).
For example, these uniform block parameters are NaN.
layout(std140, column_major) uniform _ub_params_vec4
{
vec4 _ub_param0;
vec4 _ub_param1;
vec4 _ub_param2;
vec4 _ub_param3;
} ub_params;

As long as I tried,
- Not all but some draw calls can be read.
- It has not happened on other phones/chipset.
- No OpenGL Error.
- It can read uniform parameters.

Could you tell me something that might be the cause?
Thanks.