Controlling multiple IKEA Fyrtur Smart Blinds - Not behaving

Hi all.

Recently bought a Fyrtur Smart Blind for our lounge and was really impressed! Adding it to the Hub (v3) was easy and have now set up a few automations for it (opening at sunrise etc…)

I then decided to buy another 5 blinds for all the lounge windows. Again, adding them all to the hub was easy going and they all seemed to behave.

UNTIL… I made a scene to open or close ALL the blinds. Some just didn’t respond at all, and sometimes one (random) of the six blinds would only open/close slightly. It did sometimes work, but only maybe 1 out of 10 times running the scene.

I’ve now spent 2 days pulling my hair out trying to figure out whether it may be a range issue or something else, but I’ve hit a brick wall and now thinking about taking them all back to IKEA.

The blinds are about 15 metres away from the main hub, but I have paired two “Tradfri Signal Repeaters” to the hub , more or less at equal steps between the hub and blinds (without the repeaters they simply don’t work). There are also several Tradfri Sockets throughout the house, as I know these also act as repeaters.

But I’m starting to think it’s not a signal/range issue, it just seems to be when I try controlling more than 4 or 5 blinds at one time, then it gets upset.

Can anyone offer any advice?
Also, Would it help to get a Tradfri gateway and using that as a “middle man”?