I can't completely answer your question, as I am rather new to flashing ROMs myself, but I will try. Getting an OTA update is similar to putting a new ROM on your phone. When installing new ROMs, it is best to wipe cache and Dalvik cache, due to sometimes part of that cache still 'thinks' the old ROM is still in existence. Not wiping this cache, along with keeping all user data, is considered a 'dirty' install. This can cause errors (possibly even an error in power consumption). I will be honest, it may not fix the issue, but it is worth a try.
When installing any new ROM, all developers suggest wiping all data and cache for the best installation.