To delete parallel constraint in sketch mode of Creo Parametric 3.0

It is easy task to delete parallel constraint in sketch mode of 

Creo Parametric 3.0?

First example
While modifying sketch, it is really impossible to delete parallel constraint in sketch mode

Second example
1 Newly build sketch, easy delete first set of parallel constants

2 Then imposible to delete second set of parallel constaints

Extruded cut feature and unwanted web wall

Extruded cut feature and unwanted web wall

Creating ring
- Revolve solid to create the ring
- Revolve cut to create grooves inside the ring
- Round to create rounds inside corners of the ring
- Chamfers
- Extrude cut to create holes
- Extrude cut to cut wall between grooves - the result are cut and thin wall inside the ring.

Finally after restructuring features in model tree, the strange wall automatically disappears.