diff --git a/CHANGELOG.md b/CHANGELOG.md
index a365e3dbf3..7054d61902 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@
 
 * Specify the content type when calling back to Astro with JSON to render an area. This is required starting in Astro 4.9.0 and up, otherwise the request is blocked by CSRF protection.
 * Fixes `AposBreadcrumbSwitch` tooltip prop that is supposed to be an object, not a string. Object returned from the shared method `getOperationTooltip`.
+* Uses `modalData.locale` in `AposI18nLocalize` component. Fixes watcher on `relatedDocTypes` not being properly triggered (uses data and methods for more control instead).
 
 ## 4.23.0 (2025-10-30)
 
diff --git a/modules/@apostrophecms/i18n/ui/apos/components/AposI18nLocalize.vue b/modules/@apostrophecms/i18n/ui/apos/components/AposI18nLocalize.vue
index 538f26424e..a9b26a437c 100644
--- a/modules/@apostrophecms/i18n/ui/apos/components/AposI18nLocalize.vue
+++ b/modules/@apostrophecms/i18n/ui/apos/components/AposI18nLocalize.vue
@@ -3,6 +3,7 @@
     class="apos-wizard apos-i18n-localize"
     :class="{ 'apos-wizard-busy': wizard.busy }"
     :modal="modal"
+    :modal-data="modalData"
     @esc="close"
     @inactive="modal.active = false"
     @show-modal="modal.showModal = true"
@@ -325,6 +326,10 @@ export default {
       required: true,
       type: String
     },
+    modalData: {
+      required: true,
+      type: Object
+    },
     shouldRedirect: {
       type: Boolean,
       default: true
@@ -419,6 +424,7 @@ export default {
       allRelatedDocs: [],
       allRelatedDocsKnown: false,
       docTypesSeen: [],
+      relatedDocTypes: [],
       searchField: {
         label: this.$t('apostrophe:searchLocales'),
         placeholder: `${this.$t('apostrophe:searchLocales')}...`
@@ -488,13 +494,6 @@ export default {
     isBatchMode() {
       return this.batchOptions.enabled;
     },
-    currentLocale() {
-      // We need to grab the locale from the modal data, because it can change
-      // while in modal (switch locale in editor modal).
-      // Exposing `modalData` property breaks the internally used AposModal
-      // component for some unknown reason, so we need to use the attrs.
-      return this.$attrs['modal-data']?.locale ?? this.moduleOptions.locale;
-    },
     action() {
       return this.doc.slug.startsWith('/')
         ? apos.page.action
@@ -518,32 +517,6 @@ export default {
         .filter(locale => !this.isCurrentLocale(locale) && this.canEditLocale(locale))
         .length;
     },
-    relatedDocTypes() {
-      if (this.isBatchMode) {
-        return this.getRelatedSchemaTypes(this.batchOptions.checkedTypes);
-      }
-
-      const types = {};
-      for (const doc of this.relatedDocs) {
-        if (!types[doc.type]) {
-          types[doc.type] = {
-            value: doc.type,
-            count: 0,
-            readOnly: false
-          };
-        }
-        types[doc.type].count++;
-      }
-      for (const type of Object.values(types)) {
-        const baseLabel = this.plural(type.value);
-        type.label = {
-          key: 'apostrophe:typeWithCount',
-          type: this.$t(baseLabel),
-          count: type.count
-        };
-      }
-      return Object.values(types);
-    },
     relatedDocTypesField() {
       return {
         name: 'related-doc-types-to-localize',
@@ -611,17 +584,6 @@ export default {
           }
         }
       }
-    },
-    relatedDocTypes(newVal) {
-      if (!this.isBatchMode) {
-        return;
-      }
-      for (const item of newVal) {
-        if (!this.docTypesSeen.includes(item.value)) {
-          this.docTypesSeen.push(item.value);
-          this.wizard.values.relatedDocTypesToLocalize.data.push(item.value);
-        }
-      }
     }
   },
   async mounted() {
@@ -631,6 +593,7 @@ export default {
     if (this.isBatchMode) {
       this.wizard.step = this.visibleStepNames[0];
       this.wizard.busy = false;
+      this.setRelatedDocTypes();
     } else {
       try {
         this.fullDoc = await apos.http.get(
@@ -659,6 +622,40 @@ export default {
     }
   },
   methods: {
+    setRelatedDocTypes() {
+      if (this.isBatchMode) {
+        this.relatedDocTypes = this.getRelatedSchemaTypes(this.batchOptions.checkedTypes);
+        for (const item of this.relatedDocTypes) {
+          if (!this.docTypesSeen.includes(item.value)) {
+            this.docTypesSeen.push(item.value);
+            this.wizard.values.relatedDocTypesToLocalize.data.push(item.value);
+          }
+        }
+        return;
+      }
+
+      const types = {};
+      for (const doc of this.relatedDocs) {
+        if (!types[doc.type]) {
+          types[doc.type] = {
+            value: doc.type,
+            count: 0,
+            readOnly: false
+          };
+        }
+        types[doc.type].count++;
+      }
+      for (const type of Object.values(types)) {
+        const baseLabel = this.plural(type.value);
+        type.label = {
+          key: 'apostrophe:typeWithCount',
+          type: this.$t(baseLabel),
+          count: type.count
+        };
+      }
+      this.relatedDocTypes = Object.values(types);
+
+    },
     normalizeConfig() {
       if (this.isBatchMode) {
         this.toLocalizeChoices = this.toLocalizeChoicesBatch;
@@ -710,7 +707,7 @@ export default {
       return this.wizard.step === name;
     },
     isCurrentLocale(locale) {
-      return this.currentLocale === locale.name;
+      return this.modalData.locale === locale.name;
     },
     canEditLocale(locale) {
       return !!locale._edit;
@@ -1158,6 +1155,17 @@ export default {
       }
       this.relatedDocs = relatedDocs;
       this.wizard.busy = status;
+
+      for (const doc of this.relatedDocs) {
+        if (!this.docTypesSeen.includes(doc.type)) {
+          this.docTypesSeen.push(doc.type);
+          if (apos.modules[doc.type].relatedDocument) {
+            this.wizard.values.relatedDocTypesToLocalize.data.push(doc.type);
+          }
+        }
+      }
+
+      this.setRelatedDocTypes();
     },
     wait(time) {
       return new Promise((resolve) => {
@@ -1180,7 +1188,7 @@ export default {
         this.wizard.values.translateTargets.data = [];
         return;
       }
-      const sourceLocale = this.currentLocale;
+      const sourceLocale = this.modalData.locale;
       const targets = this.wizard.values.toLocales.data;
 
       let response;