have you recently cleaned the sensor or changed mouse feet? if not. clean your surface with alcohol pads and same with the bottom of mouse and dry for 10 minutes.
Then unplug mouse and uninstall razer synapse, then restart computer. Plug mouse back in, USe a different USB port, and test. If all ok, install synapse back.
If this does not work, open up a RMA or check for firmware update in synapse, maybe it's corrupt.
sorry for the bad grammar, i was in a hurry.