Testing for new vfs cache mode features

This happens when no data has been read from the download thread for 5 seconds. It is a normal part of how the vfs cache works.

This is probably indicative that you need to use a bit of

  --vfs-read-ahead SizeSuffix              Extra read ahead over --buffer-size when using cache-mode full.

If --buffer-size isn't enough time for the reader to start up again without skipping. This buffers to disk so you could make it 512M and rclone would read up to 512M ahead of where you've got to.

You could also try increasing --buffer-size also (the default is 16M) if you made it 64M that wouldn't be excessive. Remember --buffer-size is buffered in RAM though, so don't make it too big!