Slow network performance

I’m reminded of this post Wired Network Slow - Wireless Fast - #18 by sid6581 where it seemed like there was an issue between a Vero4K+ and a Synology NAS.

In that case, an iperf3 between the Vero4K+ and a (wired) PC showed good figures but when it was between the Vero4K+ and the Synology NAS, the throughput was both disappointing and unstable, which is what you seem to be experiencing.

So, if possible, try iperf3 between the V4K+ and a PC.