[vbat99]

Not sure what is happening there, I do not have Plex.
I suggest you scape a new movie, import it into Plex, if there are no actor images, then make a Copy of the nfo and move it to a safe place, Then rescrape actors and import again into plex.
If the actor images appear, can you compare the original nfo and the recently updated nfo to see what differences there are.

If there are differences, please zip them, upload somewhere and PM me a link please. 

I did what you asked.  The first scrape on the NFO looks like this:
 
<actor>
        <id>0000000</id>
        <name>Patton Oswalt</name>
        <role>Remy (voice)</role>
        <thumb>
        </thumb>
        <order>0</order>
    </actor>


Upon scraping the actor roles specifically, the NFO turns to this:


<actor>
<id>0010872</id>
<name>Patton Oswalt</name>
<role>Remy (voice)</role>
<thumb>http://image.tmdb.org/t/p/original/dq3uNmTB7r8XTtadV3OD3N7LqV6.jpg</thumb>
<order>0</order>
</actor>


I tested it out again with another new movie. Same thing happened above. If you still need the actual NFO, let me know and I'll send them to you.

Odd, I would check the Actors tab in Preferences. I only have Save actor thumb to .Actors folder Selected.

Or, start with a clean MC, by renaming the Settings folder to Settings.orig
Start MC and add a movie root folder, and scrape a single movie. Check the nfo for actor image url