Cluster detail can not be displayed in report.html for FPGA opencl sdk v19.1.0

Hi, I have recently upgraded to FPGA opencl sdk v19.1, the new feature added in report.html is really helpfull for optimizting designs.

But I have encountered one problem that some of the cluster view could not display the internal details as others, and it only shows a "container" in report.html as follow:

Normally, the cluster looks like this:

What does the "container" mean ? I have not found any information in the official guide.