Air carrier flight crew reported the ACARS messaging was intermittently inoperative during pre-flight. After extensive consultation the flight crew printed all the necessary DG documents which made the crew legal to depart.

Narrative

We received our Planned Dangerous Goods PNF during the preflight / ACARS initialization.We were having difficulty receiving our Final DG PNF just prior to pushback; so we coordinated with ramp personnel; operations; load planning; and dispatch. Nothing was working.Finally; I called the Chief Pilot and while talking to him; I just randomly sent an ACARS code DG" and then received the Final DG via ACARS; but it did not contain the standard message to confirm the receipt with the acceptance code.After continued discussion with the Chief Pilot; he noted that we should just send a acceptance code and see what happens. I did it 3-4 times and never got the FINAL DG message. The Chief Pilot noted that the FINAL DG was not required per the FOM. We only needed to send the DA before releasing the parking brake. I verified this in the FOM as well. The FOM also doesn't state that we ever need to get a FINAL DG which we normally do when sending the acceptance code. The FOM is a bit confusing here.So; after considering all of this; I kept the Planned and Final DG; printed a copy of my sent ACARS acceptance code message from the Messages Sent Log; then wrote down the Chief Pilot's name and time on the printout. I wasn't trying to make up my own SOP; but with the nature of this anomaly; my communications with all entities; reference to the FOM; the only other option was to have the Dry Ice pulled of of the aircraft which in my opinion may have resulted in additional process limitations and further confusion. The Chief Pilot; myself and my FO felt confident that we were legal per the FOM as it is currently written.We (myself; FO or Chief Pilot) have never seen this before. The following day; we had more DG and the process worked as it normally does. We are not sure if this was a glitch; what normally is a fairly simple process became any but simple. Also; the FOM guidance regarding the FINAL DG needs to be clarified so that we know if it is required or not before we takeoff or even at all.The only other thing that may have played a role in this is that we were delayed by an hour getting to the aircraft. I wonder since ACARS was initialized possibly after the Final DG was issued that this is what created the anomaly."