We don’t limit the size of the upload, but we have run into issues where, if the upload takes more than an hour, the credentials time out and the upload fails. Typically we see this with files bigger than 1GB. What size are you trying to upload?
For the worklets, we download the file before the script runs, so that it’s available in the directory to be referenced by the worklet (or the required software policy execution command). I would think that an interruption in connectivity would be similar to the computer being offline when the policy kicks off. That would mean it would fail to run the script at that time and would attempt again next time the policy is set to run.