Ethernet access to local devices on network very slow but Wifi fast

I have just gone from a FritzBox router to a brand new Netgear XR500 with latest firmware. The internet speed for devices on my network both ethernet and WIFI is great however when I try to access some local devices on the network (Hikvision camera, smart phone with app acting as a web service) the speed can be very bad - but the catch is only when accessing via a device connected by Ethernet.

- When trying to connnect via a PC (Windows 10) to the device directly with IP address using ethernet the page will either not load at all or take around a minute to load and be broken CSS wise which indicates it didn't load fully. If the camera loads it only loads one frame and nothing else and shortly after times out.

- Only devices on ethernet suffer this problem. The same or different device attempting to access these devices via WIFI connects fast without any issue.

- I've tried another machine (Windows 7) with a different ethernet cable plugged into a different port of the router and the same issue. Again if I use WIFI on that machine instead it can access the other device fast.

- From the PC with ethernet I can ping the trouble device from command prompt and each packet returns relatively fast (<20ms)

- Connections from this PC using ethernet to these devices was super fast before switching the router. Nothing but the router has changed

- The PC with ethernet can transfer fast to another Windows machine on WIFI via copying over the network, perhaps that uses a common port or something? I'm assuming these apps use a random port.

- I've tried factory reseting the router but it didn't help.

I've Googled, read these forums, done all sorts of tests and haven't been able to work out whats wrong. Any ideas or should I just ask the manufacturer/ retailer for a refund for a faulty product?