Throttle or display malfunction after installing mirror or accessories on the handlebar
The mirror or the accessories are rubbing throttle's moving parts causing the issue
Move these parts and create a reasonable clearance with throttle.
If there is no physical contact between installed items yet the throttle or controller has issues or not working then check for magnetic parts near throttle. Throttle works based on proximity hall effect sensor hence, any magnetic interference nearby can affect the hall sensor.
A magnetic steel screw can cause this.
Make sure you put enough space between throttle and newly installed item.