May be because GroupWatchPct is set to 30 by default, and MedWatch is set to 20. MedWatch is checked against self as time to med or not and GroupWatchPct is for Other group member's to check and see if other group members need to med.
Looks like GroupWatchOn in your ini file needs to be 1|20 or MedStart needs to be 30. GroupWatchOn and MedStart have to be the same, and everyone in group must lineup with eachother or you will have some group members never sitting to med, when others think they should be medding.
I will have to talk with Maskoi and see how he wants to fix this.