i , i+1 , i++ are generally integers and used to count up for "something". I'm not sure you should be using them like that in  F_PROFILE(f, t, i+1) as i may be the surface ID: check the macro.Â
In a steady case you're trying to update a boundary at each iteration so effectively you're changing the problem. If there's no damping you may find you oscillate around a value until the solver fails.Â
Rather than trying to write ever more complex code, take a step back and figure out exactly what you're trying to acheive. Can it be done by running a model and manually altering a value to then run it again?Â
You are navigating away from the AIS Discovery experience