In order to control matter devices you need a matter controller. These Google devices act as matter controller: Nest Hub (1st/2nd gen), Nest Hub Max, Nest Mini, Nest Audio, original Google Home/Mini speakers, Nest Wifi Pro, and the Google TV (4K) streamer. The Dirigera hub acts as a matter controller, and Home Assistant also acts as a matter controller. When you commission a matter device to a matter controller we say that the device joins a matter fabric. A single matter device can join up to five fabrics. When a device is joined to more than one fabric (multi-admin mode) it has to manage these fabric memberships separately. Many devices on the market have a bad multi-admin implementation and can at most join two fabrics before they behave strangely. When I asked you to factory reset your device and then only join HA, I wanted to make sure the device is in clean state, and make sure it doesn't suffer from a bad multi-admin implementation in that situation.
In addition to all that the IKEA devices use Thread as a transport layer, and hence a Thread border router (TBR) is needed. These Google devices act as TBR: est Hub (2nd gen), Nest Hub Max, Nest Wifi Pro, and the Chromecast with Google TV (4K model) (in addition to being matter controllers). Dirigera Hub acts as TBR, and HA can act as TBR. Usually each eco system (google, apple, samsung, ikea, HA) would create their own Thread networks, and manage them along with their matter controllers. But it doesn't have to be like that, specific combinations of TBRs can form a unified Thread mesh. This is desirable because when un-unified each Thread network will eat bandwidth from your precious 2.4GHz spectrum. The outcome in that case also is that it canbe hard to tell which device in which Matter fabric uses which Thread network.
All this can contribute to error states. So, fiddling with multiple fabrics and maybe even multiple TBR can make error analysis complicated in the first place, so reducing complexity