fix

Author: Rich-Harris

packages/svelte/src/internal/client/dom/blocks/boundary.js

@@ -111,6 +111,10 @@ export function boundary(node, props, boundary_fn) {
 
 				if (suspend_count++ === 0) {
 					queue_micro_task(() => {
+						if (suspended_effect) {
+							return;
+						}
+
 						var effect = boundary_effect;
 						suspended_effect = boundary_effect;
 
@@ -149,14 +153,20 @@ export function boundary(node, props, boundary_fn) {
 					return false;
 				}
 
-				if (--suspend_count === 0 && suspended_effect !== null) {
-					if (boundary_effect) {
-						destroy_effect(boundary_effect);
-					}
-					boundary_effect = suspended_effect;
-					suspended_effect = null;
-					anchor.before(/** @type {DocumentFragment} */ (suspended_fragment));
-					resume_effect(boundary_effect);
+				if (--suspend_count === 0) {
+					queue_micro_task(() => {
+						if (!suspended_effect) {
+							return;
+						}
+
+						if (boundary_effect) {
+							destroy_effect(boundary_effect);
+						}
+						boundary_effect = suspended_effect;
+						suspended_effect = null;
+						anchor.before(/** @type {DocumentFragment} */ (suspended_fragment));
+						resume_effect(boundary_effect);
+					});
 				}
 
 				return true;