One of my BAH bookings I noticed did this last week. I did some detective work and it’s because my MAN>LHR>FAO in which I had a 1 hour 25 minute connection has now moved from T5 to T3, hence an automated system flags it as invalid now due to longer connection needed, so effectively BAH will have to refund me what is just a deposit anyhow.

it does look silly though. I have a hotel and a return flight, but nothing to get me there!

I can’t be bothered calling BAH for a booking at Easter! They automatically refunded me when a similar thing happened earlier in 2021, so no point clogging up the phone lines I don’t think!