Hi all - I've been reporting this error on the sony forums since I bought the TV last October 2015 and moved to BT from Sky. however, it seems to me that the issue is Sony and not BT.
I have 49X8309 and the BT Ultra box.
Periodically and randomly, the picture statrs to judder / jitter. The only way to resolve is to switch the tv off / on. This seems to "resync" the tv again. Switching the BT box off / on doesn't help.
It seems to be slightly better since a Feb 2016 upgrade but still occurs multiple times per week on all channels (SD/HD/4K).
Good News for anyone experiencing a problem with picture judder on their Sony UHD TV's. Sony have now put a fix in place for this and you can find more information on this link