Interferences when using WiFi 2.4 GHz and Bluetooth are possible e.g. when there are two devices which disturb each other. This is different to having only one device that has both radios enabled and therefore must not interfere with itself…
At least the latest release notes have this to say:
Fixed an issue that was preventing the user to change the Wi-Fi frequency band, when the manual choice was made and the phone rebooted afterward.
Have you checked whether your access point has reverted to 2.4 GHz only or not?