It's only inviting 4 because the max group size is 5. You need to invite those then convert to raid. I usually invite my first 4, then convert to raid then open up jamba and invite the rest via the Jamba button. As far as the following goes, i've had that problem where 1 or 2 toons in the raid didn't follow the Jamba master, usually re-setting your master via Jamba, breaking follow and then following again usually fixes that.