Great news.
I suspect that iDrive have changed a timeout, or maybe transfers are taking just a little bit longer because the server has got busier which is tripping the timeout threshold.
I could make a quirk for iDrive reducing the default value, or I could just reduce the default value as I think it is probably too high. However having a high value is good as this is not an often used API and 3rd party providers often have bugs here (eg Chunker: uploads to GCS (S3) fail if the chunk size is greater than the max part size)