Firefox starting in safe-mode when launched via keyboard shortcut

Describe the bug
I have mapped Firefox to option-w but it only starts in safe-mode this way. Switching to Firefox when it already runs works though. Same behavior with Thunderbird.

Screenshots

Device information:

  • Type of Mac: Macbook Air 2018
  • macOS version: Mojave 10.14.5
  • BetterTouchTool version: 3.05