I have this problem and I'm new to LumenRT so I can't tell if it's a problem with my program version (18.104.22.168).
When I increase the display quality more than1 star, the texture of the carpet disappears, what am I wrong?
Can you please share the .lrt file with us ?
You can use this link to upload the .lrt LumenRT file
Will have a look what is the issue at our end.