Hi @Youngdavid, Since that your Flash2 is not rooted, what i can advice is to do a factory reset and check if anything will change and if the issue will still persists. Please try this
Warning: this action will erase all your personal information, files and downloaded apps.
In power on state:
Click " Settings" -> " Backup & reset" -> " Factory data reset" -> " reset phone"
In Power off state:
1) Long press Power Key and Volume Up Key
2) Use volume up key to select "Recovery Mode" and use volume down key to confirm.
3) Press Power Key and Volume Up Key together twice to enter recovery mode.
4) Press volume down key to select Wipe data/ factory reset
3) Press volume down key to select " Yes---delete all user data".
Warning: this action will erase all your personal information and downloaded apps.
If the issue still persists, i highly advice to have it checked to the nearest service center on your location. Godspeed!