Jaheira sometimes stops following the group in act 3. Another of her problems can be that she follows, but is not counted as a full member of the team, so you cannot give her buffs like Minthara's "Soul Branding" and she will not automatically enter the fight when the rest of the gang rolls initiative.
I hadn't heard of either of those problems happen with Wyll before though. His main problem seems to be either his romance scenes having low priority compared to other camp scenes and his current dialogue after defeating Ansur being a mess if his dad is also alive/ not yet saved.
