Launching Non-Steam DCS via Steam

Before anybody asks, because it's convenient to keep them all centrally located. Should be obvious, but I know somebody will ask @@ :P

And it's already on an SSD, other expected question ;)

MOVING ON

Bizarre little thing here, it's inconsistent, but sometimes (most times, actually) when I launch DCS through Steam, it pops up a box saying "instance is already running" or some such jazz (as many times as I've seen it, you'd think I'd remember the wording better). Usually, it is only one or two boxes. But... On rare occasions (like five minutes ago) it may open a few dozen boxes. Needless to say, this is somewhat of a pain in the ass.

Only thing I can figure, is that because DCS takes a while to load, Steam thinks it's not working, so it tries very... VERY hard, to repeatedly open it. Or something. But that's weird, because normally a game will simply fail to start. It ONLY does this with DCS, making me think there is something weird between the two.

Does anybody else run into this? Is there a fix? Or do I just have to continue cursing under my breath? I've been dealing with this for several years, technically, and only now became irritated enough to ask about it :D

-edit

Note, that it ALWAYS successfully starts. That isn't the issue. It works every time. It just pops up 1 or more of these boxes, and sometimes dozens, I have to tab out to close them all (assuming it doesn't do it while the game is already booted and I can't see them, in which case I have a present waiting when I log out)

I've never had this fwiw.