New password not accepted during first login reset after running Migration Assistant

I have used migration assistant to transfer from a 2019 MBP (running Sonoma) to a 2023 M3 MBP. The (main) admin user account transferred fine. The two non admin user account have been transferred and after some adventures trying to work out what random password Migration Assistant set (hint: perhaps capital I and lowercase L should not both be candidates for use when the system font is sans serif) I am left in the following position when I try and log in to either of the non-admin accounts:

• I can log in using the temporary password
• I am prompted to change it (as this is the first login)
• Absolutely nothing is accepted

Note that the passwords match, the dialogue box just shakes and the reset fails. The only option is to his cancel and return to the login screen.

This is running Sonoma 14.2.1.

Is there a way I can give this a kick that will result in the normal first-login behaviour for each of these users being run? Are they any side effects to changing the user password to be either the current temporary password or the new password they would have been set to? Are their keychains locked with the current temporary password, the old password or something else? I need to ensure I don't lose the keychains or the end-to-end encrypted appleid-related data with those accounts. (I still have the old device but I do not want to migrate again/reinstall because (a) it's a pain and (b) it was over a month ago and the main account is different now and (c) life is too short.)