I noticed an issue with th e fill tool when using the bitmap fill type and "nearest" quality. The replications seem to "round down" in an unexpected way along the x and y-axis along the origin of the first replication (see attached image). The pattern used here is a 2x2 pixel image with the top left pixel set to black, the others white. Both the top and the bottom fills use the same image with the same settings, except that the top image uses the "nearest" quality, while the bottom one is set to "lanczos3" - I guess it is obvious what I'm talking about.
The issue is not as dramatic, as you can simply move the origin out of the visible area, but nevertheless.