It doesn't replicate it every time on start up
If it doesn't replicate every time, it could be a Mozilla Service, like the update checker. Download "
Autoruns" from SystemInternals, run the .exe (
no installation necessary) and first ensure in the menu (
under "Options") that the tick in front of "Hide Windows entries" is set. (
Otherwise you will have an overwhelming number of entries).
Then go to the "Services" tab. I am quite sure you will find a Mozilla entry there (
see screenshot, I put the tab and the line in yellow). You can completely remove the service (
by righclicking the line and selecting delete) or just remove the tick in front of the line, to test (
the Service will not be launched at the next startup).
While you are there, also look into the other tabs, whether there are no entries you do not need (
especially the "Logon" tab). In the "Scheduled tasks" tab, there is also a Mozilla entry, which is aimed at ensuring that another browser does not "highjack" the postion of Firefox as your default browser and which you do not necessarily need (
if Edge is taking over you will find out at your own and you can set Firefox again as your default browser).
And there might be other entries in other tabs. I often look into the the first 6 tabs or so (from Logon to Drivers), I think it's better to leave alone the others (
especially "Image highjacks" and "Known DLLs"; don't delete the entries there). If you decide to act on an entry, always first remove the tick only to test, of you don't see any impact after a few days, you can then delete it completely.
If you want to know the meaning of the colors in "Autoruns", please see screenshot 2 (
I don't remember where I got it from).
Good luck