Even though 2FA being enabled seems to settle the issue, it could still be a conflict that only manifests during the regular login process. I am working on the assumption that this is the usual login page included with WordPress rather than another user-management plugin?
Firstly, try disabling 2FA and navigate to the login page causing problems and inspect the browser console. Are there any red errors or failed script/page loads reported? If you want to use screenshots to illustrate problems directly, please try Snipboard which will provide you with links to paste here for me.
Secondly, it might also be worth installing the Health Check & Troubleshooting plugin which allows you to disable any/all plugins and switch to a default theme, but only for your user to prevent downtime for other site visitors. This should allow you to identify if there are any previously unseen conflicts elsewhere between Wordfence and another plugin. Try having Wordfence enabled without anything else, and then if the problem seems to have resolved, reenable plugins one-by-one until the problem reoccurs.