To reproduce:

1. Use a system that commonly uses middle-click as a mechanism for pasting, such as most Linux window managers.
2. Enter some text in a VE wikitext-mode edit field.
3. Select some text elsewhere in preparation for pasting it.
4. (optional) Focus the edit field with a left-click.
5. Middle-click in the edit field at the location where the test should be inserted.

Expected behavior:
The text is inserted at the location of the middle-click.

Actual behavior:
The text is inserted at some other location. If the edit field did not have focus when middle-clicked, it inserts at the very beginning. If the edit field did have focus, it inserts at the current cursor position instead of at the position middle-clicked.

Workaround:
When this happens: curse at VE/Flow, press Ctrl-Z to undo the bad insertion, left-click at the desired insertion point, then middle-click to paste.

If you anticipate it happening before attempting a middle-click, you can skip the first two steps in the workaround.