I'm now seeing what you're talking about, which isn't exactly as you first described. The behavior is happening only when the last-active window no longer exists, either because of close-on-complete or by manually closing the window. It's not happening when you're clicking back-and-forth to/from a dcc window that remains open.
If the last active window no longer exists, $lactive returns $null rather than the name of a window that no longer exists, and $lactivewid returns 0 rather than the WID of a non-existent window.
Yes - apologies for not having described it correctly first time. I can probably code around this bug by using the ON CLOSE event.
