I apologize for my late response.
Unfortunately there is not much we (Viber) can do to help, as official representatives
The fact that the problem was solved on CM, but is now present again on the new ROM you're using, suggests that it is indeed a problem with the ROM (and not Viber). We recommend that you contact people on that thread, or in other threads here on XDA, who might have had similar issues. At this stage we (Viber) will not be able to suggest a solution for this problem, caused by the Custom ROM
An official representative of Viber Media (Viber app.)