Clients just got an IRS notice for that situation....1095-A showing last 3 months blank for columns B and C as they continued coverage through the marketplace all year, just stopped with the advance premium credit in Sept.  After verifying w/ them for full year coverage, I entered the SLCSP for last three months, and IRS computers having fuss about it since it 'doesn't match'.  Leaving it blank decreases the credit they were getting.

Not sure the chances of successfully getting a correct 1095-A but told clients how to explain it in their reply.