Problems with logging in.

We have been using this plugin for a long time, but recently we have been experiencing a problem where, after entering the login page, I am automatically taken to the website backend, sometimes as the LAST logged-in user, not as myself. After selecting one of the functions in the backend menu, the user switches to my account. I don’t understand why the hidden login page is not displayed, but I am automatically switched to the backend on the computer where I access the website every day.

The system seems unstable because different users are being switched.

What can I do about this?