Your interpretation of the log isn't entirely correct.
The log tells that rclone was unable to store/write the files in the cache
.. because it was unable to download them
.. because the Icedrive servers reponded with HTTP error code 429 (Too many requests)
...ten times in a row
...when rclone requested the files
...with minimum request speed (1 request every 2 seconds)
and yes the cache is located on your local system.