Have you included the custom [Updated] field in your database? 
Yes, I have. And this field never causes any problems. It is always updated when running the allrovi script. 
 Are there any fields not updated from external sources that do not cause [moddate] to be updated when changed?
I am sorry. Could you please restate your question for me? I have a problem to understand what you mean.
The issue I'm seeing, BTW, seems to be sort of the opposite problem. My [moddate] seems to be updated just by putting a record into edit mode—without changing anything. 
Yes, I discovered this, too, but only for some movies and not for all. At the "Living Daylights, The" for example, the [moddate] field is not updated when entering the edit mode.  
I am stumped  
Update: Now, I am getting officially crazy. This morning, when removing the entries from the sub-genre field for “licence to kill” in the edit mode, the [moddate] field was properly updated. But after rerunning the allrovi script, the [moddate] was not updated. I repeated these steps several times and checked carefully the [moddate] field.  So, I am sure that this wasn’t an error in observation. 
Now, I did this test again and now it is working properly. The [moddate] field is updated in both cases: after removing the content from the field in the edit mode and after running the script. 
After this I created a new database and added as custom fields [updated] and [sub-genre]. I added the “licence to kill” movie and ran the imdb and allrovi script. Then, I removed the entries from the sub-genre field and closed the edit mode… The [moddate] field 
 hasn’t been  updated  

 The update with the allrovi script worked fine including an update of the [moddate]  field. I repeated the three times and results were always the same. 
I don’t see any pattern in this. I think I will throw my computer away and move into the forests.