This question has come up a few times recently, so I recorded the video below to show the issue and how to solve it in TBC.
The problem posed is that you import a data file from e.g. Trimble Access and you then process feature Codes to create the linework drawing and to appropriately tag all the data as Include In Surface or not. Having processed the feature Codes, you then select all of the data and make a surface model. At this point you realize that the surface is not forming quite right in certain areas because of feature codes that were incorrect in the field. So you go into our point data properties and change the feature codes on the appropriate points and then you re run Process Feature Codes to update the drawing.
The problem is as follows. On doing the above, the second time you process feature codes, all linework is deleted and recreated regardless of whether or not the feature coded points of those lines were changed or not. The side effect of this is that those new lines are not a part of the surface model that you created from the original linework after the first Feature Code Process. It can be a little tricky to spot that this happened, because the triangulation changes may be subtle (the points are still in the surface, it is the breaklines that got removed. If you turn off the Feature Lines and Turn On Breaklines in the Surface properties the change is more evident.
To solve the problem, you can add the imported file (JXL or SPJ from Access or Siteworks) to the surface model and this will make sure that whenever you process Feature Codes for that “Data Block” that the linework that is generated from the Processing will be included in the Surface Model. The reason for this is that the Linework created from processing a Data Block is added to the Data Block automatically, so if the Data Block is included in the surface, then the Linework generated from processing the Data Block is also added to the surface automatically.
The video below shows you the problem and how to address it in TBC v5.21