DXB/BRS/DXB over FRA still showing AED13580 (approx £1835) on the LH website for end May.
I just put this itinerary in to
www.lufthansa.com, and it popped out at £722. (In Economy)?
Sun 25 May 01:35 Dubai 06:05 Frankfurt LH631
Sun 25 May 09:05 Frankfurt 09:55 Bristol LH4960
Mon 2 Jun 06:30 Bristol 09:15 Frankfurt LH4965
Mon 2 Jun 14:50 Frankfurt 22:45 Dubai LH630
That's not the lowest available fare. The lowest should be QLNRAE, at £289 / AED2120 plus tax (so about £545 inc. taxes).
Try running it again. It might give creedence to my theory that LH.com caches fares and only calculates them after it's been hit a few times. Or maybe it's borked on the lufthansa regional website in DXB?