Large Downloads become .ZIP files that won't expand

We are using the PR4100 to collaborate on video projects remotely. We are able to download files or folders up to about 4 or 5 GB just fine using, but anything larger is downloading as .zip files, and they consistently have the error when unzipping:
Unable to expand file into “Downloads”. (Error 2 - No such file or directory.)

This has our workflow dead in it’s tracks, and the PR4100 24Gb was quite an investment to make this specific thing possible. Does anyone know what’s causing this problem, or how to address it? Thank you!