Resolve "(File Drop Mode) : File sent from the user in file drop mode is not received by another user"

src/components/messages/messageMixin.js

@@ -2,6 +2,7 @@ import QuickReactions from "./QuickReactions.vue";
 import * as linkify from 'linkifyjs';
 import linkifyHtml from 'linkify-html';
 import utils from "../../plugins/utils"
+import Vue from "vue";
 
 linkify.options.defaults.className = "link";
 linkify.options.defaults.target = { url: "_blank" };
@@ -58,7 +59,26 @@ export default {
       }
     }
   },
+  beforeUnmount() {
+    if (this.validEvent) {
+      this.event.off("Event.relationsCreated", this.onRelationsCreated);
+    }
+  },
   watch: {
+    event: {
+      immediate: true,
+      handler(newValue, oldValue) {
+        if (oldValue && oldValue.getId) {
+          oldValue.off("Event.relationsCreated", this.onRelationsCreated);   
+        }
+        if (newValue && newValue.getId) {
+          newValue.on("Event.relationsCreated", this.onRelationsCreated);  
+          if (newValue.isThreadRoot) {
+            Vue.set(newValue, "isThread", true);
+          }
+        } 
+      }
+    },
     originalEvent: {
       immediate: true,
       handler(originalEvent, ignoredOldValue) {
@@ -70,7 +90,7 @@ export default {
           });
         }
       },
-    },
+    }
   },
   computed: {
     /**
@@ -164,6 +184,11 @@ export default {
     },
   },
   methods: {
+    onRelationsCreated(relationType, ignoredEventType) {
+      if (relationType === "m.thread") {
+        Vue.set(this.event, "isThread", true);
+      }
+    },
     ownAvatarClicked() {
       this.$emit("own-avatar-clicked", { event: this.event });
     },