Similar issue... have a LH ticket booked without my middle name that I am trying to credit to my A3 account which does have my middle name.

LH is unable to add the A3 number in advance because of the name mismatch but they claim I can do so at the airport.

Will I have issues getting miles credited to A3?

I had the reverse issue with another family member in the past where the ticket had their middle name but their A3 account did not. That was easily corrected by sending A3 a copy of the passport with my middle name but not sure they would be willing to 'remove' a middle name on my account in this case.