There's another possible explanation.
Disclaimer first: I only have
knowledge of Rockman 1. But Rockman 2 is largely based on Rockman 1 code.
In Rockman 1, there's a variable,
CurrentStripeEndType at RAM address $26 responsible for marking the type of the end of the current stripe. 0=right, 1=up, 2=left, 3=down. It may also be 4, but the circumstances are unknown.
But the point is, the variable is reused. Besides being loaded from the map data, it's sometimes also set during enemy AI handling.
I don't understand fully yet how it works, but it could be what's responsible for this "shutter tech". Somehow, an interference with enemy actions and Rockman's actions cause the game to get wrong reading for the
CurrentStripeEndType and as such, the game will do a right-scrolling when it's supposed to only do down-scrolling.
If my theory is on the right tracks, this glitch may exist in Rockman 1 as well.