From my point of view, I wouldn’t consider it fair but they seem to only base their pricing on Bloomberg. That thing proved unreliable time after time again, I watch the community quite often and it caused multiple similar situations. I’m not sure you can hope for much more, normally, if you can prove that only their platform had an anomaly, they should reimburse you. But they can claim it’s Bloomberg’s fault (which is true, maybe they should price their instruments from multiple sources?), so they might not offer much more on top of that…
I just checked another broker and the price is pretty flat at that point in time, on both the sell and buy charts so no stops were triggered there. It is definitely something wrong with Bloomberg as it can’t get their pricing right sometimes.
I hope you will get a higher reimbursement. 