superhostingvip I've never come across any software in the hosting industry that was bugless on a major version release. Never, not from any control panel, not from any operating system. Even basic little WordPress plugins come out with major version updates riddled with bugs on nearly every major release.
It's highly irresponsible to make such an upgrade thinking everything will work fine. Bugs are expected.
12 hours during the first days of such a major update is also a really short time, especially for such a niche/unimportant issue of unzipping large files in file manager.
How would I react? I would see that my issue is niche, I'd tell angry customers I screwed up by not following the most basic principles of updating in production, I would see there have been dozens of comments made already detailing issues in the file manager and know that my own niche issue is likely backlogged behind much more critical issues.
In the meantime, this niche issue is extremely simple to work around. The tools are already there even for customers to solve it on their own, just ftp in and use cli. If customers don't know how to do it, then obviously the sysadmin can handle such niche requests until the bug gets fixed. This is not a "my customers are completely shut down and can't operate until it's fixed", at most it's simply a minor inconvenience, and you've blown it way out of proportion.