Launching a 2nd Firefoxportable instance launches the 1st instance

i have many different firefoxportable in different folders. but recently this keeps happening whereby launching a 2nd firefoxportable will launch the 1st instance and thus a blank new window of the 1st instance instead of the 2nd instance.

Closing the 1st instance will resolve this but this shouldn't be happening. why is the 1st instance interfering with the launch of the 2nd instance?

these are the settings in all of my firefoxportable dirs:

[FirefoxPortable]
FirefoxDirectory=App\Firefox64
ProfileDirectory=Data\profile
SettingsDirectory=Data\settings
PluginsDirectory=Data\plugins
FirefoxExecutable=firefox.exe
AdditionalParameters=
LocalHomepage=
DisableSplashScreen=true
AllowMultipleInstances=true
DisableIntelligentStart=false
SkipCompregFix=false
RunLocally=false