the issue is that cyclical flag can monitor variables and IO but not call functions like ABS. it can evaluate readily available info that is already in variables. but it cannot call programs or functions to get the values.
just rewrite your expression from
$CYCFLAG = ABS(BoxTypeSensor - BOX_SENSOR_LATCH) > 0.1 ; error
$CYCFLAG = ((BoxTypeSensor - BOX_SENSOR_LATCH) > 0.1) OR ((BoxTypeSensor - BOX_SENSOR_LATCH) < -0.1) ; works
Yessss! I wouldn't have guessed that was the issue, but you're perfectly right, it was the ABS function that was causing the error. I've now rewritten the expression as you've stated, and there are no more issues.
Thank you both SkyeFire and panic mode, I really commend the work that you do on here
Have a great day.