Why does my Viber 'last seen ' jump to the past ?

[Android Central Question]

Why would someone's last seen status jump from 'last seen 5 minutes ago ', show that time for several hours ( let's say last seen at 10 am), to ' last seen yesterday ' and than back again to 10 am ? That's going back in time. It also hapen that it went to a date one week in the past, showed that for several hours and than came to actual time when we were communicating. This is puzzling, please help.