Fazer oil level sensors are known for being a bit temperamental, they either just stick or corrosion get in or on the contacts causing a short. It's normally sorted by a simple clean up of the connectors, some need removal and a clean. The latter is best done during an oil change, some do fail that said, I've never replaced one.
The sensor is really just early warning of low oil level and they're pretty sensitive 100ml ish from on to off. The slight glass is the best way to check your oil level, best checked 5 mins after you've ridden it, half way is good. Fazer are really good on oil a healthy engine should use almost nothing between changes.
Pull off the contractors, if there corroded clean them as best you can, both the wire end and on the sensor. Reconnect if the light goes out bingo sorted, put some silicon grease on them and recover, job done, drain out the oil, if the oil is good/new or still a few 1000's to go be needing changing tip it back in 3/4 way up the sight glass. Ride check 5mins after you've stopped.
I'd also not recommend starting sorted bikes every week, all your doing is encouraging moisture in the engine, which over time can start to emulsify the oil and it breaks down the oil faster. In my opinion best way to store a bike, service the brakes, chain, levers, cables etc, pinch the fuel line and run the bike until it stops, hook up the Optimate (or similar) and leave it. It will be fine like this for couple years, I kid you not.