sorry to hear about the possible issue with the BMW. If it were me, I would not be afraid to ride it the 20-30 miles to the dealer and have them check it. If it turns our you are on the hook for the repairs, then you will still have a great bike. The cost of the repair will be forgotten over time.
Don't over think it.
As for ST1300's, I had a 2007 non-ABS. What a fantastic machine! The only real issue I had with it was the heat. On a hot summer day the tank would get so hot it would burn you if you touched it. As long as temps were <85, it was fine.