Hi Ahmed,
The forces are repeated because the muscle goes through via points, these via points works as "needle eyes", so there will only be a force present if there is a kink on the muscle line of action on the node.
In the current model pelvis and sacrum should be considered as one segment. We are in the process of fixing this by moving muscle attachments which are currently located on the pelvis to the sacrum segment.
Best regards
Søren