If you mean that the face touching the block disappears, then this is correctly behaving the same as a vanilla glass block.
Otherwise, I cannot see any problem. Can you tell me what platform you are using (Windows, Android, etc.) with steps (which block, which faces, etc.) to help me recreate the issue. Thank you.
Otherwise, I cannot see any problem. Can you tell me what platform you are using (Windows, Android, etc.) with steps (which block, which faces, etc.) to help me recreate the issue. Thank you.