Don't perform pathfinding on other player's rulers

src/foundry_imports.js

@@ -168,7 +168,7 @@ export function measure(destination, options={}) {
 
 	this.dragRulerRemovePathfindingWaypoints();
 
-	if (isToken && isPathfindingEnabled()) {
+	if (isToken && isPathfindingEnabled.call(this)) {
 		const from = getGridPositionFromPixelsObj(this.waypoints[this.waypoints.length - 1]);
 		const to = getGridPositionFromPixelsObj(destination);
 		let path = findPath(from, to, this.draggedEntity, this.waypoints);

src/pathfinding.js

@@ -8,6 +8,8 @@ let cachedNodes = undefined;
 let use5105 = false;
 
 export function isPathfindingEnabled() {
+	if (this.user !== game.user)
+		return false;
 	if (canvas.grid.type === CONST.GRID_TYPES.GRIDLESS)
 		return false;
 	if (!game.user.isGM && !game.settings.get(settingsKey, "allowPathfinding"))