Need help on VR2 joystick circuit board Failure analysis

The attached pictures shown its both side, any one can help to figure out the principle or function blocks? it is lost function without reason, that two components are not the fault location.

1. I didn't see any memory battery, how can it probably look like ？
2. I'm trying to modify the PAD let it's start button be remote controllable, and soldered few wires on the board, the solders were OK, because I checked it many time after soldering.
3. the failure just comes without reason, and I have checked every connections ARE good, (actually it was running just before fail.).
4. the the symptoms of failure is when power on, there are 7 battery gauge LEDs and 5 speed LEDs all are flashing, according to the error code, it is connection or joystick fault.and suggested to check:
1) if the battery charger is connected to the power base.
2) if the charger harness fuse has blown.
3) if all controller connections are plugged into the power base properly.

did you check the 3 items the error code suggested?

the picture do not show enough detail
take pictures from above instead of from the side
get close ups
3 may be enough - from the two notches down, from the two notches to the glare, and a picture of the top section without the glare

specify what the wires are attached to

if there is a memory backup battery, it will probably look like a small cylinder, anywhere from about 3 mm diameter to 15 mm diameter and 2 to 4 mm thick.