My Passwords vault is repeatedly failing

Deep within the settings of my iPhone, iPad, and MacBook Air is an app called passwords. When enabled, it automatically saves and updates my passwords on dozens of websites that require a unique password. It has been reliable until the last few weeks where it invariably has failed, on every program that requires a password. This has happened before with auto fill-in the feature that puts your personal data in fields that require name, address, telephone number etc. There I’ve learned to use the auto fill in and then erase the last letter and put it in manually. Now this is happening with passwords but because the passwords are randomized by Apple, I don’t always know what the last character is. Why is it failing? Could it be that I have too many saved passwords?