I am not quite sure if I have spotted something, but whenever SMP detects a new metar.rwx file, the cloud shadows disappear for some seconds or a bit longer. They reappear once the new weather is rendered, with a little delay.
I have 300 MB of VRAM left and FSGRW is running on the same machine (latest build).
Log.txt provides no hints, despite the phenomena can be pinned to the entry whenever SMP detects a new metar.rwx file.
Otherwise RWC and FSGRW work in harmony and joy [emoji16]
I missed to provide a log.txt, but will do that tomorrow of the day after. Just on the pace with family for some ice cream...
Cheers , Jakob