Download issues with low speed connections on ASM

This has nothing to do with slow speeds. ASM is not designed to inspect files bigger than 50Mb.

You can increase this limit by changing the max_filtered_html_length setting. - check the support article here:

https://support.f5.com/csp/article/K10007

As these are downloads from your own website I assume these are trusted files, so technically speaking you don't need to process them with ASM. In such case another option is to simply configure ASM to ignore these large file extensions (e.g. .ZIP extension) or disable ASM using an iRule - you will find many examples here on DevCentral