Broadcom bluetooth/wifi chips ran out of firmware hot patch ram slots long time ago. Company seems to be too cheap to respin the rom mask with all the fixes baked in. From what I remember even brand new iphone x ships with no room for BT firmware patching.

RECON 2019 - Reversing and Exploiting Broadcom Bluetooth (Jiska, Dennis Mantz) https://www.youtube.com/watch?v=96Mi8_9ABCc

35C3 - Dissecting Broadcom Bluetooth (jiska mantz) https://www.youtube.com/watch?v=4_nI9ok7iQg