[Therion] Spikes at passage ends: Loch

Hi This may have been discussed and resolved before, apologies if so. Is there a reason why loch models do this? The passage to the left of SK1, SK2 extends about 40m beyond the survey line, more or less horizontally, and so I have extended the plan and elevation scraps to draw the explored, but not surveyed, passage. (I think the elevation scrap has no effect on the model, but I can understand the reasons for that) For some reason the last little bit of the 'freehand' passage model extends up to the sky. Is there a solution? I have in the past tried to use the 'point dimensions' entity in plan scraps, but not always with success. Thanks bruce