How did you want to proceed? The error indicates that it timed out, and your experience (20+ minutes to scan the file) also supports that.
Do you want to know how to configure the timeout (if it is configurable)?
Do you want to know how to prevent the timeout (exempt the file in someway)?
Well, what we were hoping for was for an answer as to why it would take that long to scan the file. If I perform a manual scan using a pc and say another competitors AV, it takes less than minute.
But I suppose a workaround to prevent the timeout would be ok.
the reason why it takes so long for the file to be processed is that the Composite Opener is enabled. MWG can look inside CAB files and will extract every single file inside and send it to the AV engine for scanning. For an archive with more than 700 MB this can take some time.
If you disable the Composite Opener (by Default it' s under Common Rules) the AV engine will only scan the CAB file itself without looking what's inside. This is much faster.
please note that turning off the Composite Opener will reduce the level of security MWG provides to you, because files are no longer scanned in depth. I would recommend to whitelist the Composite Opener for this specific download.
It is nothing special that there are some files which cause MWG to take pretty long to extract. You cannot compare the extraction time to what a desktop AV or a different vendor need, because MWG by running as a Gateway has to use different technologies for scanning. As an example it has no option to rely on an "on demand" Scan, which is provided by a desktop AV.
If you believe there is an issue with the file you could report it to technical support and we will investigate if there is any chance to speed up the extraction process.