Got this official respond from Viber:
Thanks for contacting us and sorry for the inconvenience.
This is a known issue which affect some devices. We are presently working on the solution. you can expect an update on version 3.
Would be great if everybody experiencing this could star the bug over at Google: https://issuetracker.google.com/issues/112385921
Thanks. What about wifi issues and general lag when battery is low?
This sums up my reaction to all the people complaining about "silent mode" when its simply been renamed to "Priority mode" with an added app whitelist feature, "Lollipop sucks", "daily driver"/"stability", comparisons to other OS', and the constan...
EVERYBODY gets lag, even Google acknowledge this. It's a bug in Lollipop.