Hey GI, welcome to the forums! Can you show us a pic of when you have it clamped into the WEPS vise when you are having this problem? a pic from the side preferably… If it is getting a wider bevel at the tip there could be one of two issues:
1. You may not have the blade positioned properly in the vice (front to back); if you haven’t already, look under the “resources” tab at the top of the WEPS website and check on the wiki, there should be an article in there on “finding the sweet spot.”
2. It could be due to the grind of the blade and it getting thicker near the tip. If this is the case, the bevel will get wider unless you change your sharpening angle near the tip, or re-grind the primary grind/face of the blade and thin it out near the tip.