In some random cases the specified partial factors for anchor capacity (using the Design Approach tool) are not taken into account in the calculations.
Carefully inspect your output results to see if this might be happening for your situation. You might also inspect the properties of the created ULS material set in Output (via Project > Material information) to see if the partial factor is taken into account or not. Also see the example below.
If you find that this issue is happening in your case, you might manually create a separate (ULS) material set for your anchors in which you reduce the anchor strength. Then replace the SLS anchor set with the ULS anchor set in the ULS phase.
This issue is solved since PLAXIS 2D2012.01