NSA310S - Data Access Problems

Hi all,
I own the NSA310S since two years and now I am facing problems with the data access.
I have some movies and TV shows on my NAS and use the fireTV stick to stream them on my TV.
Recently, I can no longer access the movies via the TV stick or my pc. I can see the data but it is not loading. After a while it sometimes works or when I unplug the NAS/router/fireTV stick, but not always and it seems quiet arbitrary to me. I am not sure if it has something to do with the latest firmware I downloaded (V4.75(AALH.2)C0)
Does anyone have similar problems or can someone help me?

Thanks,
JuZu

#NAS_Feb_2019