I have no direct experience but I have a couple of thoughts.
Does the new charging unit work besides the timer element? I guess that there are no compatibility issues - but it might be worth checking with the installer / manufacturer regarding the set up ?
Can you try it out on a 3rd party charger - car park / supermarket? Does it charge OK and give better range?
Regarding range, much like mpg, manufacturers claim numbers much higher than you will normally achieve. In this instance (as with so much of our renewable sources) it will be based on a calculation of the theoretical full capacity with no allowance for losses and inefficiencies. Temperature, the local terrain and number of passengers will also affect the range.
Either way - it's best to ensure that the problem is logged with your dealer just in case it turns out to be a later known issue.