When my Bluetooth peripheral device has both HID and MIDI services, the iOS Bluetooth host repeatedly sends different "Control Opcode: LL_CONNECTION_UPDATE_IND" to the peripheral, updating approximately every 100ms.
The Bluetooth peripheral cannot handle such high-frequency update requests and typically disconnects with an error 0x28. My Bluetooth device uses the NRF52832 chip, and I have communicated with NORDIC and replicated this issue.
This problem only occurs on iOS 26; it does not happen on earlier versions. I think it might be caused by the HID service in iOS requesting faster connection parameters for low latency, which then gets erroneously reverted for an unknown reason, leading to repeated competition and entering into a deadlock.
Here is the communication record with NORDIC: https://devzone.nordicsemi.com/f/nordic-q-a/124994/ios-26-bluetooth-disconnect-issues
This is the screenshot captured using the Bluetooth sniffer: