Can someone explain what the problem was, what the dyno results were and how it was fixed?

It was essentially just completely erratic. The accuracy was +/- 10HP in my opinion. I saw the same thing with a friend's Miata that they have dialed in and it was all over the place on this dyno.

+10 -10 from run to run? Or some cars were +10 or -10 from a previous Dynojet?

My personal experience was as follows.
My car had been dynoed at Buttonwillow the previous month at 137 hp and 137 TQ following the prescribed procedure in the rules on a Dynojet. This engine was a fresh build early this year with used pistons, new rings, bearings and a frshened head. I did start with an 88 high compression engine. Oil was Mobil 1 0-40. Also using a stock 944 muffler.
At Sonoma I did not dyno on the Thursday test day as I felt my engine would be fine since I had a 3 hp cushion. On the Friday dyno compliance run my car tested at 143hp and 144tq average.
After changeing oil to MolyLube 20-60 and setting DME to #4 I tested at 135 hp and 134 tq. I left it there for the rest of my 944spec sessions. I was also running in PTE so I would switch DME back to the 0 setting for those runs.
After the Championship race the top 3 dynoed again and my car tested at 131hp and 132 tq.

Now in light of the dyno issues we have been going through and as much as I dont like the dyno due to the inconsistencies. I believe that it is still better than what Spec Miata is doing. They have a set of rules to control the build of the motor. If any one has been watching the SM class for a while you know that the HP has been constantly increasing over the years. At the inception of SM about 10 years ago a good motor was 105 hp. Thay are now pushing 125hp. All with STOCK engines. They spend way more than we do on motors. We may not have a great system but I think it is workable.

A possible solution may be to include a compliance dyno run with our entry fee for Championship races.
MCE who runs the dyno in NorCal region charges $60 for 3 pulls. I imagine that NASA could arrange a discount for a guaranteed number of compliance runs for the bigger events. That way we will know right away if we need to tune up or down to stay in the range.

I got to deal with the same dyno thing at both Nationals. I was very close to the line at Atlanta with 138hp on the final trip to the dyno.
In northern California the air was significantly cooler as was the ambient temperature, so we expected a bit more power. I dyno'd 139, 141, then 144 (with 147 tq!) This seemed unusually high and was concerning. I added a 52 mm restrictor (the smallest one we had) and paid to get back one the dyno the next morning and had gained 2 hp!!! WTF! We changed from redline 40WT to Valvoline VR-1 Full synthetic 2050 Racing oil. I also changed the ECU setting to #3 (which I never even knew about before this weekend). The car definitely felt bit slower, but I was still pretty competitive for 3rd. After the national race, I dyno'd 128,131, and finally 134? Seemed super odd.

Dan it was great to meet you and your crew at Sonoma. Hopefully we will get to do it again next year at Laguna. Heck I am even considering the East Coast Nats too.
May not be able to bring fish tacos to that one