Sounds like the unit’s housing probably needs to be opened up and the interior inspected for damage, loose connections, cold solder joints that have cracked due to the shock of dropping it, etc. If it’s under warranty you could try claiming a repair but more than likely if there is any indication it’s been dropped, the manufacturer will not cover the repair. If you are interested in trying to repair the unit yourself you may need initially some form of “spudger” tool(s) to open the unit. This site and others like Amazon have kits, such as the following, which can be purchased.
Essential Electronics Toolkit
That all said and done, you may find it is easier and more economical in the long run to just buy a new unit. Wish I could be of more help.