BTT filament sensor keeps showing "empty" after a few seconds

Just installed the BTT "smart filament sensor" and it seems to be working, shows up in the main dashboard and says "detected" once filament is inserted. But after a few seconds of printing, it toggles itself to empty. If I slowly feed the filament through by hand while a print is going, it works as expected/pauses the print and shows empty once the filament runs out, so it seems like it's just expecting the filament to move faster than it actually is. I tried playing with detection_length, but various values between 1 and 100 don't seem to change anything, what else can I change?

My config file if it helps any:
[filament_motion_sensor btt_sfs]
switch_pin: !PG12 #plugged into ESTOP4
detection_length: 7.0
extruder: extruder
pause_on_runout: false
runout_gcode: PAUSE