That might be a problem with network speed. How are the Vero 4K+ and the data source networked (WiFi, wired Ethernet)? Is your source defined as an SMB or NFS source within Kodi, or are you using something like autofs or fstab to mount it at OS level? Have you tried copying the file onto a USB stick and connecting directly to the Vero to see if that plays any more smoothly?
Running iperf3 might give you some info about network performance: