Active sprites rendered one pixel to the right of actual location

(Up to Tricks and glitches (first generation))

The glitch occurring at the half-pixel level (or "Hires" mode) in WinUAE 4.0.0.

In WinUAE, the sprites for worms, projectiles, mines and in-motion gravestones can be shifted to the right by one pixel, resulting in an inaccurate representation of the object's current location. Once the object has stopped moving or is no longer active, the sprite shifts back to its "real" location.

An extreme version of this glitch is also present in FS-UAE, a multi-platform Amiga emulator, causing the entire horizontal space aligned with an object to jiggle or sheer.

This glitch can appear to affect sprites at the half-pixel level, thanks to the Amiga's two default resolutions - Lores, which renders more-or-less square pixels, and Hires, which renders pixels at half the width, allowing for more horizontal detail.

This glitch also affects the brush in Graffiti mode.

Cause

This was caused by WinUAE's incomplete or inaccurate subpixel emulation. A partial fix for this issue at the time could be found in the Resolution toggle in the Display settings in WinUAE. By default, this is set to "Hires (normal)". By changing this to "Lores", the issue would be resolved, with the downside that the main menu will be rendered at a lower resolution, and this may also affect other Amiga games, as well as Workbench.

Changing the Resolution setting to SuperHires results in a variant of this glitch that occurs on the quarter-pixel level, with Worms that come to a stop appearing to "settle" into a particular position that can be off by a quarter-pixel.

The issue is no longer present in WinUAE as of version 4.1.0.