Comment 11 for bug 1875475

> Unison failed: Uncaught exception Failure("input_value: ill-formed message")

I met exactly the same issue after "downgrading" the unison to unison_2.48.4-1+b1_amd64.deb on Ubuntu 20.04

And the workaround is indicated by @velmont, that to delete the files in ~/.unison
But I got an extra issue after deleting the files:

Fatal error: Warning: inconsistent state.
The archive file is missing on some hosts.
...
Please delete archive files as appropriate and try again
or invoke Unison with -ignorearchives flag.

So I need to run unison with `-ignorearchives` flag once to recreate the states, then the whole issue is fixed.