I currently own two NH 276 balers. I like them better than any other baler I have run. The stokes per minute are higher on this baler than the newer ones. It will out bale a NH316 or JD 336.
In wheat straw loading wagons( stacking not a thrower wagon) behind the baler I have put 275 bales an hour on the wagons for a whole after noon. It was a nice long field and windrows from a 20 foot combine head.
Things for you to do:
1) Check the resticters on both sides of the bale case. I run three sets all of the time.
2) Check the side play on the plunger. I have seen a bad plunger roller cause banana bales.
3) Make nice big windrows. These balers bale better if you keep them full.
4) Like the others have stated. You move the adjustable feeder fingers AWAY from the chamber for more hay on the opposite side.
These things should get you back to having good square bales. If not check how the hay is being raked. Many times one side of the windrow will have most of the hay in it and the other just the ends bent over. Walk across the windrow and see if it seems to compress evenly across the whole width. Had that happen to me when we started to rake with a wheel rake years ago. Had the rake set too narrow and one side had more hay in the windrow than the other. Made getting a good square bale hard even with the round baler.