How to spot a seam in a repeating pattern in Krita
Use Wrap Around Mode at two scales to tell a broken brushstroke from a strip of empty space running through the repeat.
A leafy tile looks balanced by itself. Repeat it across a wall and a stripe suddenly appears. Inspect it at two scales: a stem that stops at the edge and a corridor between motifs need different fixes.
Draw across the boundary
Open a 512 × 512 px document for this exercise. On a new layer, draw a stem towards the right edge. Turn on View → Wrap Around Mode to see adjacent copies of the tile. Extend the stem across the boundary. If its width changes at the join, try a single stroke across it rather than retouching two ends separately.
Look for a rhythm from further away
Zoom out until roughly three rows and three columns are visible. If the leaves all stop short of the boundary, the gaps can line up into a stripe. Move a small leaf across the edge and compare with the original before filling every gap. Save the layered KRA file and export just one tile as PNG. Repeat that PNG at its native pixel size in the destination app. A line that appears only at certain zoom levels may be a scaling artefact. The 512 px size is for the exercise, not a print specification.
Krita Manual: Preparing Tiles and Textures · Krita 4.2 release notes, May 29, 2019