Disable automatic thumbnails creation

Hi,
I have a question about how the automatic thumbnail creation works.
My device is a "WD My Personal Cloud" which I use together with a Samsung SmartTV over WiFi. Everything works good, quite simple navigating thru folders, pick a vid and hit play, even FFD, Skip, REV works (not great but suitable).

So, my problem is mainly when watching episodes of a series, that I dont know what I already saw. All thumbnails are ceated and it looks like I saw every episode.
When using an external USB-HDD on my TV thumbnails were only created fo episodes I watched.

So, my question is:
Is it possible to "patch" the WD My Cloud Twonky Server that the thumbnails are only created after playing a movie (so that it acts same as when using my tv with an external HDD)?

Thanks for any suggestions.