Briefly, I’d suggest using iPerf3 to check your network speed (and retries) between the Vero and your NAS. Does the same thing happen with 1080p titles ?
See
Sometimes it is important to check the network performance between your OSMC Device and the device providing your media (NAS, Server, PC). Especially when you are connected via wireless the throughput variations can harm you viewing experience.
This short How To should give you the required information how to install iperf3 and how to run the respective tests. When doing these tests it is suggested to have a simple setup (single switch between Sender and Receiver and avoid other traffic on the …