I have taken no explicit actions to clear caches on my phone.
Now, it is even worse - I am even unable to paste my strong password into the box anymore so I have to type it out instead.
Thanks for taking a check of that for us @sdrew1.
It could also be worth checking the permissions for the app to see if there's anything there that could be preventing this from saving these details long term.
If you can, it's worth testing this with a different device as well, to see if the same issue occurs. This can give us an overview if it's linked with a device setting or something wider.
Peter