Hey Martin,
I also have a save state for the Level 05 rivets. It's defined as the first frame of the preceding "stacked monkeys" screen. I conducted a series of experiments and noticed 2 sets of consistent results, depending on how the save state is loaded.
Method 1
I loaded the save state (dkong-r.sta) directly from the command line:
mamep106-vc dkong -state r
After pressing the [Enter] key, I supplied no other inputs. The results were identical, 10 times out of 10.
Method 2
I loaded DK from the command line, without the save state:
mamep106-vc dkong
After pressing the [Enter] key, I loaded the save state using [F7]. As with the first method, I provided no additional inputs. The results were again identical 10/10. However, it was a different result than that obtained from Method 1.