yesterday i seen, there is a firmware update to 0.0.32
control chip fix
You should open a support case with Garmin and ask them to replace your Neo 2 non drive side housing.
The .32 firmware has nothing for Neo 2 owners, only Neo 2T.
Like you, my Neo 2 only worked with version .15 and worked very well. When updated to .18, no more cadence. While I was able to resurrect the cadence function by adding a paperclip to extend the crank arm (and have been mostly happy since then) I just wanted you to understand that the option to replace the non drive side housing is available.
The cadence sensor is glued to the housing, so unfortunately, you cannot just replace the sensor board.
Still no answer from support. I year ago I decided to go for the NEO 2 because I thought problems could be solved by the firmware but I now regret my decision, not to buy the 350€ cheaper obsolete model then. Because I never get the firmware updates working...