I am not trying an end-on-end combination. The fare components I am referring to are the same origin/destination (one is ART, the second is FRT).
matrix ita fails to pull these fares and instead pulls IATA YY fares.
It's a similar story when using an amadeuspower engine.
If no stopovers, it pulls FRT for both. If with stopovers in SIN it pulls the EK YRT that has unlimited stopovers.

I am guessing this is to do with the 'most restrictive' conditions and thus sees the combination of ART/FRT as invalid.