The only solution that works 100%:
Before every flight and before opening MSFS:
Navigate to C:\Users<YourUserName>\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalState\packages
Then delete everything in the "justflight-fstraffic-module" folder.
Start MSFS and it will rebuild those files and should work properly.
I am using FS Traffic daily and had 1/10 times no arrival traffic as the module stopped working after takeoff. The above solves it.