Have you tried a full reset to Factory on the Sky router, then a sequential reset of other items.
I have found that the Sky Q router can get easily confused and even with a recent minor change it required a reset to factory on the sky Q router to sort.
The main Sky Q TV box needs hard wiring to work reliably, the mini boxes require a strong wifi signal to work.
Yeah it looks like you had made a mashup that unsurprising didn’t work.
Keep it simple. You often can’t simply mix and match Ethernet network devices together and expect to work without clearly understanding the network function they are performing. Routing, switching or bridging. These are all very different and distinct functions.
There should be one router only. Its switch ports should connect to your hosts, wifi access points or another switch.
Some Mesh systems also act as a router… you seemed to have your mesh system router connecting to your SkyQ router and its switch ports. If so that will not work, without using advanced equipment and some IT know how on configuration of these advanced devices. Most consumer stuff won’t support this.
Remember keep it simple… ensure you have ONE router only… have that router at the interface between your internet access and your LAN.