Joystick works except for other buttons when shell is closed

I got my Nintendo Switch since its launched in March 2017. Just a year later, the LED indicator and the SL+SR buttons on my left joy-con stops working (aside from the joy-con drift problem). I did not care that much since I only play single player games and mostly on my Switch Pro Controller.

Now that I have my own family, I wanted to play Switch with them. So I tried to fix the left joy-con by replacing the SL ribbon cable and joystick. I knew I was successful because the LED indicator lights up again and the SL + SR button are being detected. My problem is when I try to put back the shell. If the joy-con shell is closed tightly, only the joystick is being detected, the rest like the d-pad, L, ZL, etc. stops working. Loose up the shell slightly, all the buttons will work again.

Can you help me with this problem? I would appreciate your support on this.