Hi all, I can also confirm this bug! I am a new Fairphone 2 user since two days. As my device wont boot into recovery from LineageOS 15 I found another thread about that bug here. It seems that this bug can be worked around if the flash light is turned on before the reboot. The bug might have the cause in the new camera module. I can confirm that with flash light turned on while rebooting my device boots into recovery and here is the thing: does not loose the paired Bluetooth devices!!!
Maybe you can test this on your device? Interesting would be: Does the problem only occurs with the new camera module? Does the workaround with turned on flash light works for you?