Premiere needs better file recognition to be able to relink proxies encoded externally or internally. understanding _Proxy endings an din general relink proxies automatically, more often.
Adding my shrieking voice to this thread. What ABSOLUTE nonsense it is that a project created on one computer cannot open on another computer without a host of these audio channel mismatches. It should just work.
I've got 60+ files that I need to manually reingest and send back to my fellow editor in the hopes that we can share the project easily.
For those dealing with this in 2022 I have found a solution that does not require you to re-ingest your proxies. Upon opening your project, offline the proxies and wait for Premiere to load. Once in the project, go to where your media bin is and right click to select "Attach proxies." If you have your proxies written to the same drive in a separate folder like I do, link to that folder and you should be re-attached. Hope this helps!