Some ideas if you haven't tried them already:
-Space the remotes a few inches apart
-Try angling the Outlaw remote 20-45 degrees vertically in relation to the URC remote (try both upward and downward).

I find my Outlaw remote is most accurate when I aim well below the IR receiver.

Do you have the mxeditor software for the MX-900?
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Outlaw Audio Model 976 / 7700 / Ultra-X13
B&W CM9, CM Center, DS3 (side), DM303 (back)
Blue Jeans Cables (XLRs, Canare 4S11 Bi-wire, HDMI)
Tivo Bolt, Xbox Series X, Panasonic ub820, AppleTV 4k, LG C765P
Roon, Allo Digione Signature, Sonore MicroRendu, Uptone Audio LPS-1, Peachtree Audio Nova 150
GIK Acoustics Soffit Bass Traps, 244 Panels, Monster Bass Traps, QRD7 / Polyfusor Diffusers