XR1000 Spotify tracks pause before playing next track

I've had a strange problem with my XR1000 router and Spotify. There's a bit involved, so I'll start with the symptoms.

When I use Spotify Connect, to stream music to my Anthom MRX1140 receiver, every track will pause for about 5 to 10 seconds about 20 seconds before the end of each song/track. After the pause, playback will resume, followed by the next track. If I have a playlist, it will do this for every track, but the last track will play without any pause. So it only happens when there is another tack.

eg. There are 3 tracks, each is 2 minutes long. The first track will play for 1min 40 seconds, pause for 10 seconds, then resume. The second track will do the same. The last track will play normally.

It doesn't matter if I use my phone, PC or laptop, it always has the same problem.

My setup is the XR1000 WAN connection to Modem, Ethernet port 1 connected to a 16 port Gb switch. The Anthom receiver is connected to the switch, and so is my PC. Phone obviously uses XR1000 wifi, all on the same network. I've tried using PC to stream Spotify to the receiver (no wifi) and also tried connecting the receiver to wifi (no switch) and the problem is the same. I've also tried removing the switch all together, still no luck.

Here's the strange part. I have an old Netgear r7000 so I tried that. The problem goes away instantly. I also tried a friend's Asus router and again there's no problem. So the XR1000 definitely has something to do with it. The next strange thing is I tried an older Denon receiver, and that does not have the problem.

There is something not interacting well between the XR1000 and Anthom1140 receiver. Both work in a different setup, but together they don't. If I can get the XR1000 to play once with the Anthom, I'd like to keep it, otherwise I'll be forced to buy another router.