¯\_(ツ)_/¯ the CRC error could be due to network or host issues. And the MVPs only have one download host, so the FSO Installer can't try mirrors if one fails.
The MV_RadarIcons_3612.zip seems to be particularly prone to causing errors -- in at least one case due to being so small that it triggered a bug with my integration with 7-zip. (This bug is now fixed, assuming you're using the latest version.)
One other possibility is that 7-zip JBinding is not well supported on ArchLinux. Since this library was not written in Java, it has to be recompiled for every platform.
Would implementing multiple connections to the same server (split the file into segments and download them at the same time ala download accelerators) be hard?
Because, then if one segment fails, it can be resumed without failing the whole file, and if all segments fail, it's probably definitely a problem on the server side.
IMHO. I've been using download accelerators since... 1997? In my personal experience, that tech (multiple resumeable download streams for the same file) increase the reliability and speed of a download in 95% of cases.
Of course, if it's a headache, probably not worth the effort (although I imagine you could port one of multiple open-source Java Download Manager engines into the Installer?)
Last time I used the Installer I had to re-run it to complete all downloads, which, if I'd have used a browser + download manager I can almost guarantee I would have been able to download everything without issue.
Anyways, it's just a thought, and the Installer is a big plus regardless of all this, so feel free to ignore.