The most common reason is the browser overwriting the field due to saved LastPass data in the browser's password manager or form filler.
same thing happening with me. Every site that I have tried to open and see the password, it quickly reverts to an old password that I have used but not for the affected sites. How can I fix this?
Again, please check your browser's password manager or form filler for erroneously saved LastPass data. See FAQ linked below for major browser manufacturers.
Chrome:
Edge:
Firefox:
Safari:
Did what was suggested - no resolution. Now most of my items save the correct password when opened, but for about 25% the password immediately changes when I open the wrench.