The piston that is stuck in the down position is the Power side, which is why it won’t lift a load, thus only working on the speed side. If it’s nothing externally with the shielding catching up, it could be something internal between the piston and the cylinder wall. The downfall of this newer style is the lack of guide to keep things centered and no matter how much grease they smear on the top end from the factory, it’s going to be susceptible to wear, which can cause binding. It’s one of things I noticed when I tore down the Daytona when it first came out.
Hopefully it’s a quick fix with the shield, if not elevate the rear, remove handle assembly and pull the stuck piston straight out for inspection.