Orbi RBR850 / RBS850 – Constant IoT disconnects (Shelly, robot vacuum, etc.)

I’m experiencing persistent instability with my Orbi mesh network and IoT devices, and I’m hoping someone can help confirm whether this is a known issue or if there’s something fundamental I’m missing.

Setup:

Orbi RBR850 (router)

2 x RBS850 (satellites)

Firmware currently downgraded to V7.2.7.15

House size around 189 m2 + 50 m2 garage

One satellite has been tested both wired and wireless

Problem:

Multiple IoT devices constantly drop off the network and reconnect.

Shelly Gen3 (garage door switch)

Robot vacuum (Deebot)

In Home Assistant I see repeating patterns like:

device turned off

device became unavailable

device became unknown

This happens many times per day, often in the same time windows for different devices, which strongly suggests network instability rather than individual device issues.

Phones, laptops and TVs appear mostly fine. The problem mainly affects 2.4 GHz IoT devices.

Symptoms:

Devices disconnect and reconnect every 20 to 60 minutes

Some devices show weak signal despite being 5 to 10 meters from the main router

Devices sometimes connect to a satellite even when the main router is physically closer

Problems persist across different firmware versions

What I’ve tried:

Downgraded firmware on both router and satellites

Power-cycled everything in correct order (router first, then satellites)

Tested both wireless and wired backhaul

Removed one satellite completely

Disabled 5 GHz temporarily for onboarding

Re-paired devices multiple times

Factory reset Shelly devices

Verified signal strength and placement

None of this has resulted in stable long-term behaviour.

My conclusion so far:

This looks like an Orbi mesh, band steering or roaming issue affecting 2.4 GHz IoT devices. The devices themselves work fine on other networks, but with Orbi they continuously flap between connected and unavailable.

It feels like Orbi is aggressively steering or optimizing in a way that modern phones handle, but embedded IoT devices do not.

My questions:

Is this a known behaviour with Orbi and IoT devices?

Is there any way to force devices to stick to a specific AP?

Is there any way to fully disable band steering or roaming?

Is it possible to create a true 2.4 GHz only SSID without hidden steering?

Are there any recommended settings specifically for IoT stability?

At this point the network is fast but unreliable, which is honestly worse than just slower but stable.

Any insight appreciated, especially from others running IoT-heavy setups on Orbi.

Thanks.