When you get a chance, please introduce yourself here.
Thanks for all the details you’ve provided. We’re currently investigating the issue, and hopefully we’ll be able to improve the scanning experience soon so that codes like the ones you’re using can be scanned more easily.
Is there any way (via XML, appearance, or settings) to force the old ZXing scanner instead of ML Kit?
There's no easy way to do that. You could try disabling Google Play services, as mentioned above, but you'd need to do it on every device you use - and keep in mind Collect also relies on Play services for location, so that will affect more than just scanning.