The log shows that your Vero4K+ tries twice to connect to the router and succeeds only on the second try. After that it seems to be ok.
I see that you have already installed iperf3 on the Vero, so you need to check network performance between it and your PC. See [How To] Check Network Performance with iperf3
You also need to see how the disk performs locally. A simple command should give us an idea of the write speed:
time dd if=/dev/urandom of="/media/Seagate Backup Plus Drive/zzz.tmp" bs=8M count=100 oflag=direct
This will write 800 MB of random data to a single file on the USB drive. You can then remove the file.