After using the brush editor, the first stroke on the canvas has broken/like freezed sensors input. It's very visible on brushes using pressure-size (the outline stays at max value during the whole stroke), or with pressure-opacity (strokes has the same "random"/initial opacity for the whole stroke). Reproducible: Always
Fixed in https://phabricator.kde.org/rKRITA84fe0d80ece2c903c6e2fa1527dae53f88fa1e49