The program was unable to obtain a satisfactory estimate of the position of the dekker in the region below the trace.
The algorithm for determining the dekker position steps out from the peak intensity until the intensity falls below a tunable threshold. If the predicted edge is reached before this occurs then the lower dekker is set to this predicted value (simply calculated as half way between the orders).
TUNE_DEKTHR may be varied to adjust the threshold. It is also possible to manually adjust the status of each pixel in the profile by setting PFL_INTERACT=Y.
Martin Clayton