Key phrase is "almost like;" I think that can be ruled out (unless there is some property where convergence works differently across different inputs...doubtful).
Likewise, you can certainly count out the bayonet mount adapters, if they are made passably well. Likewise, it's composite, so the cable quality shouldn't matter. I assume the console's working fine on other displays, so count that out as well. I also assume that the BKM-21D was installed and used before being sent out - there is a possible software incompatibility between the BVM and the BKM-21D but I really doubt this is the issue.
So likely there is an issue with the BKM-21D or the way you've hooked it up.
In any case, you will want to download this and read it thoroughly (starting on page 29):
http://www.manualslib.com/download/2632 ... m-21d.html
It's free so no worries there. Good to have around even if you don't crack it open ever again (and get the BVM manual if you don't have it, too).
Specifically, you want to look at the second paragraph on page 30.
If that's not at issue, it might be termination-related. Some members have talked about similar experiences here (bottom of the page):
http://shmups.system11.org/viewtopic.php?f=6&t=48490
I hope something here is useful for you!
Oddly enough, there seem to be some traces of colour in these bands that keep running up and down the screen.
).
. Seriously, it should be for free!)
Composite is finally okay! And all I had to do was reset the card to factory settings! And I threw away hours trying to get it to work! 
