You can check the target line in the Firefox desktop shortcut (right-click: Properties) to make sure that nothing is appended after the path to the Firefox program.

Nothing unusual there, the target is

"C:\Program Files (x86)\Mozilla Firefox\firefox.exe"

Is the other profile present in the profiles.ini file as one of the choices?

• http://kb.mozillazine.org/profiles.ini_file
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Yes it is. But the one opening by default is NOT the one named bz84f5tg.default

If you aren't using the Profile Manager to select a profile then the profile that is marked as default=1 is being used. You can use the Profile Manager to select the preferred profile and tick the box to use the selected profile.

• https://support.mozilla.org/kb/Managing+profiles
• http://kb.mozillazine.org/Profile_Manager

What does "marked as default=1" mean?

What I can tell you for sure is that the profile labeled "default" in the profiles folders is not actually being used as the default.

Read the profiles.ini file in a text program like Notepad.

[General]
StartWithLastProfile=0

[Profile0]
Name=03-22-11-N
IsRelative=1
Path=Profiles/ns45iuo6.03-22-11-N

[Profile1]
Name=default
IsRelative=1
Path=Profiles/b3ddbhfr.default-3.6.8

[Profile2]
Name=dev-edition-default
IsRelative=1
Path=Profiles/gz1hmvsz.dev-edition-default
Default=1

[Profile2] is the default.