Could you provide an example of such fare(s)?
LHR-SIN on AF in first
There is a fare FGBRTLC1 that you cannot see with others tools and US-MX POS DotRes.
DotRes POS UK, 2 days ago:
KVS Availability Tool 6.0.3/Diamond - DotRes: LHR-SIN/AF/FGBRTLC1/4961 EUR]