Author here: we write zip files with the widely-used library zip.js [1], so if that's writing bad zip files, the problem is going to be widespread across many web apps. But I'd argue that zip.js is thoroughly battle-tested (current open issue count: 0) and not the cause of the problem.

[1] https://gildas-lormeau.github.io/zip.js/

Thank you for replying back with relevant details.

Are you perhaps zipping something that other zip.js apps are not? Perhaps you have stumbled upon some edge case.