Do members have right to vote according to their conscience?

If yes - why is that a problem? They stick to the overarching rule, and you should argue the rules must be amended.

If not - that's a huge problem IMO and can be summarised with "why pretend jury has any say If they must not stray from the way the case is presented and defended (knowing very well how awful public defense is and how dishonest sometimes police and prosecution can be)" and not replace it with just a judge?