I'm not too surprised to be honest. That's the problem with a bolt mechanism; it's potentially more jarring to the refill than other mechanisms. It's also not helped by the fact that the Schmidt refill is a rollerball rather than a ballpoint and therefore has a more free flowing ink. The solution would be to move to a ballpoint refill and/or change the spring to one that's slightly less aggressive.
For those that are unaware; rollerball pens use water-based inks (similar to fountain pen inks), which generally have a lower viscosity than the oil-based ballpoint pens. This makes for a smoother and more pleasurable writing experience. The downside is that they usually require a cap when not in use, to prevent the ink from drying out. They're also less versatile, as the O-pen use case demonstrates.
The Schmidt 8126 refills and their mini variants are described as capless rollerballs, so the ink won't dry out when exposed for long periods of time. I'm not exactly sure what the differences are in terms of the ink formulation to a more traditional rollerball refill, but it still flows smoothly, so is likely to be less viscous and more affected by acceleration than ballpoints.
Gel inks are something of an in between option, but I'm not sure if they wouldn't also suffer from the jarring of the bolt action.
Here is an interesting comparison of the various inks:
https://www.therefillguide.com/ballpoint-vs-gel-vs-rollerball/
