If you get these errors while using Firefox, you can fix it easily.
Here is how you do it.
1. Close Firefox. It won’t work if it’s open.
2. For Windows XP, 7, 10 etc, pull the search bar and type “firefox.exe -P”.
A window will open saying that you can create a new profile.
3. Create a new profile, name it as you like. Uncheck the last option there.
4. Close that window and open Firefox.
Everything will be like new. However, you won’t have your bookmarks or saved passwords. It’s like you have installed Firefox from scratch.
Be sure to save your bookmarks and everything. However, you can always switch back to your old profile and save them.
You should not get the errors with “props missing content”.
This issue is usually caused by your Firefox profile getting corrupted for various reasons. One can be that your PC crashed with Firefox open.