external users – Trouble with downloading a large number of files from SharePoint

I have an external partner account that wants to download a large GIS data set from our SharePoint. The data set is about 13500 files and is around 43 gb in size, and is housed within a folder. When they try to download it, it’s downloaded as a zip file, but it’s never able to fully complete, even though the browser says the download is complete. Sometimes the zip file is only a couple of GBs and won’t open.

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Other times, the download manages to get to around 20 gb, and the zip file can be opened, but half the files haven’t been downloaded and I get a bunch of text files in the zip with error messages in them.

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Each text file has an error message inside:
“This file cannot be downloaded.

ExceptionType: ZipMeTAException.

CorrelationId: 7dcb10e9-be4f-4edb-b24b-d469dcaaf844,

UTC DateTime: 1/29/2020 10:09:47 PM”

I’ve tried downloading the folder myself and never got past 20 gb before the download “completed”. Is there any reason why it’s not possible to download the whole folder, and is there a better method to download such a huge number of files that would work for an external partner?