initial reproduction

app/components/foo.hbs

@@ -0,0 +1,20 @@
+<p>
+  To reproduce the error, click open, then close.
+</p>
+
+<button type="button" class="open" {{on "click" this.open}}>
+  Open
+</button>
+
+<button
+  type="button"
+  class="close"
+  {{on "click" this.close}}
+  {{on "click" (fn this.setValue "foo")}}
+>
+  Close
+</button>
+
+<div {{(if this.isOpen (modifier this.myModifier this.value))}}>
+  Hello World
+</div>

app/components/foo.js

@@ -0,0 +1,34 @@
+import Component from '@glimmer/component';
+import { modifier } from 'ember-modifier';
+import { tracked } from '@glimmer/tracking';
+import { action } from '@ember/object';
+
+export default class Foo extends Component {
+  @tracked isOpen = false;
+  @tracked value;
+
+  myModifier = modifier(
+    (element, [value]) => {
+      console.log('running modifier', value);
+    },
+    { eager: false },
+  );
+
+  @action
+  open() {
+    console.log('open');
+    this.isOpen = true;
+  }
+
+  @action
+  close() {
+    console.log('close');
+    this.isOpen = false;
+  }
+
+  @action
+  setValue(value) {
+    console.log('setValue');
+    this.value = value;
+  }
+}

app/templates/application.hbs

@@ -1,7 +1 @@
-{{page-title "Example"}}
-
-{{! The following component displays Ember's default welcome message. }}
-<WelcomePage />
-{{! Feel free to remove this! }}
-
-{{outlet}}
+<Foo />

tests/acceptance/application-test.js

@@ -0,0 +1,15 @@
+import { module, test } from 'qunit';
+import { visit, click } from '@ember/test-helpers';
+import { setupApplicationTest } from 'example/tests/helpers';
+
+module('Acceptance | application', function (hooks) {
+  setupApplicationTest(hooks);
+
+  test('does not blow up', async function (assert) {
+    assert.expect(0);
+
+    await visit('/');
+    await click('.open');
+    await click('.close');
+  });
+});