How to cure an erratic mouse?

Your welcome, those steps cure most mouse and keyboard maladies.

Two simple things to do: clean the optical sensor and try a different mouse mat.

The following will require any USB keyboard and mouse. If you don’t have them, borrow or buy them, they are inexpensive!

• Connect the USB keyboard and mouse to the computer.
• Open System Preferences – Bluetooth   
• Un-pair the wireless keyboard and mouse.
• Turn off Bluetooth
• Restart the computer in Safe Mode per the directions in https://support.apple.com/en-us/HT201262
• Restart the computer normally.
• Open System Preferences – Bluetooth
• Turn on Bluetooth
• Re-Pair the wireless keyboard and mouse.   
• Unplug the USB keyboard and mouse and begin testing the wireless devices again.