Not sure if its password manager or not although it least temporary it has gone away turning off Password Manager.
On a windows 11 Pro using Firefox, I have been having frequent problems since mid August accessing some sites Notably Amazon. Most often site times out before displaying anything. Goes away if I clear cache but obviously that causes annoying problems as all sites need to get new sign ons and credentials.
Just tried a several hour session following Firefox troubleshooting guide, and problem appears to go away if I disable Password Manager extension. Note I also use Norton 360 and had gone thru a long troubleshoot with it to see if other components of it might be the cause.
All components, windows 11 pro, Norton 360, password manager are at latest GA levels.
Norton Password manager
Last Updated August 5, 2023