Hi Welcome to just answer.
There are 2 things you can check:-
Stylus .. this is responsible for picking up the sound
The cable that connects the pick up head to the arm. Some times they come loose and you might loose contact
Isomeone it possible to isolate the pick up head and use external pretty amp?
Well to me I think it is something to do with the amplifier on the system and we to start elimination process by separating the individual audio components.
The stylus plugs onto pick up head on many of similar systems the two components can be changed individually or together.
My suggestion to isolate the parts would help me understand what need to be done to correct the problem.