The range is only an estimate based on your recent driving style. For example, if you have been recently driving using the ICE in stop start traffic or at slower vehicle speeds, you'd be using lower gears more often, therefore higher engine revs per minute (rpm) so the car would estimate a lower range based on this type of driving. Now you do a bit of freeway driving, the car is now in top gear with a lower engine rpm. The car now thinks if we continue driving this way, then your range will increase because the engine speed is slower while in top gear so therefore using less petrol. Of course when you switch back to slower speeds again off freeway, the range will probably sharply decrease. My advice is to not take too much notice of the range, it's just a guess and usually a poor one. Just enjoy driving the car and fill up and charge up when necessary.
BUT I took it out to the dealer and guess what, it came straight off ? They ordedred a new one and replaced it. I now carry a 8 inch shifting spanner in my glovebox just in case it happens again so I get better leverage on it. I havent taken it off since then and I've just passed 2000kms on that one fill so far and petrol gauge still has 2 bars on it. I stay in EV mode all the time around town 
