Look like Smart Cover screen to me. You might want to disable it, unless you have phone in “smart cover” with a window. https://consumer.huawei.com/en/support/c...-us00753794/ If the phone is switching off randomly, I would assume there is something wrong with the power button. Since you had the phone apart, it is quite possible that you have “messed up” something. So, have another look inside and focus on the power button and its connection to phone MB.
Mode dial has either dirty contacts or is faulty. I would take it apart and clean everything accessible inside. I have two cameras with the same issue occurring “randomly“.