The reason why your system is unified after the update, fast charge is slow, this may be due to the first is the update system is not mature, may have problems in charging, there is another possibility is that you in the update process caused by the problem, resulting in slow charging, it is recommended that you download the full package to update, may fix you this problem
That's because the system is being updated, so it's cleaning up the junk. Flash charge only after cleaning the garbage.