It only does this for passwords where the login is associated with my main email address. But this is incredibly annoying, because if I were to resave the password, the actually password would be rewritten.
Check the saved passwords in your browser's password manager. If you need assistance on where to find that, list the browser that you're currently using.
It's not a bug; your browser most likely has a saved entry tied to LastPass and that is what's overwriting the fields. See FAQ:
https://support.lastpass.com/s/document-item?bundleId=lastpass&topicId=LastPass/FAQ_Browser_Password_Manager.html
I had the same problem as I now cannot view any password without LastPass writing over the password with the master password. Am astounded that LastPass let a bug of this magnitude happen.
What I am doing in the meantime is using Microsoft Edge to find the password by name and going into LastPass and adding the PWD as a note. I have 176 entries and so it is going to be a lot of work.
Tried an alternative solution that worked even less: Switched to Bit Warden and went to the trouble of exporting the password data. However Bit Waren does not have the features that LastPass has. So tried to cancel Bit Warden and probably lost $40