If that fixes the problem, then great!
But I'm having a hard time jiving "the points split up" with using Ctrl while dragging them. So I'm concerned about your report that when you try to drag 2 nodes at the same time "...the points split up..." isn't really solved. If I understand what you mean by that, this indicates that you have more than one node, occupying the exact same spot (at at least very close). So that when you select the nodes one at time, you only select the one on top. Then when you move it, the one below stays there.
If that's the case, you need to be more careful when you draw the triangle, that you're only placing one node at a corner.
Or it could mean that the triangle path was not properly closed. In that case, on the corner where the nodes split, select the 2 nodes which are either on top of each other, or very close (by dragging a tiny selection box around them, with the Node tool. Then click "Join selected nodes" button on the control bar.
Or it could be a combination of both problems. But in any case, if the problem comes back, just let us know. And also, if you could share the file, that would help us know for sure.