How to fix error 20 on 1100D canon camera - Canon EOS 1100D / Rebel T3 Digital Camera

Error code 20 is a warning of a non specific mechanical malfunction.
Most likely within the mirror, shutter or aperture mechanism, some sort of disturbance, error or lock-up has been detected. This error code doesn't specify where the exact problem is, but points to the cause being mechanical rather than an electronic gremlin. Looks like a visit to the camera repair shop may be necessary.

U have to fix this by the way of getting new button. U can get it on ebay or aliexpressm, etc. Disassemle the front side and button section, get out old button, than put new button and settle it down with trigger. And that is all! Good luck!