Updating from 4.2.8 should overall work although there where many changes from 4.2 vs 4.3 which may break your configuration.
As for the issue found by MJ Derksen it's the first time I hear about it, capturing logs or status would have helped debugging.
Overall I'd say better backup your configuration before upgrading.
And restarting clean ain't a so bad idea, subsequent updates from the 4.3 branch should be easier afterwards.
BTW, updated packages periodically made available on my github at:
https://github.com/th0ma7/synology/tree/master/packages