diff --git a/src/api/abstract/abstract.router.ts b/src/api/abstract/abstract.router.ts
index 3ff633d58b..cf81d2ae6a 100644
--- a/src/api/abstract/abstract.router.ts
+++ b/src/api/abstract/abstract.router.ts
@@ -110,7 +110,9 @@ export abstract class RouterBroker {
     const { request, ClassRef, schema, execute } = args;
 
     const instance = request.params as unknown as InstanceDto;
-    const body = request.body;
+    // A GET without "Content-Type: application/json" arrives with request.body undefined,
+    // because express.json() only populates the body on JSON requests.
+    const body = request.body ?? {};
 
     let groupJid = body?.groupJid;
 
@@ -169,7 +171,8 @@ export abstract class RouterBroker {
     }
 
     const instance = request.params as unknown as InstanceDto;
-    const body = request.body;
+    // A GET without "Content-Type: application/json" arrives with request.body undefined.
+    const body = request.body ?? {};
 
     const ref = new ClassRef();
 
@@ -208,7 +211,8 @@ export abstract class RouterBroker {
     }
 
     const instance = request.params as unknown as InstanceDto;
-    const body = request.body;
+    // A GET without "Content-Type: application/json" arrives with request.body undefined.
+    const body = request.body ?? {};
 
     const ref = new ClassRef();
 
diff --git a/src/api/integrations/channel/whatsapp/whatsapp.baileys.service.ts b/src/api/integrations/channel/whatsapp/whatsapp.baileys.service.ts
index 22839fd451..5a0725ccd0 100644
--- a/src/api/integrations/channel/whatsapp/whatsapp.baileys.service.ts
+++ b/src/api/integrations/channel/whatsapp/whatsapp.baileys.service.ts
@@ -4920,14 +4920,14 @@ export class BaileysStartupService extends ChannelStartupService {
         subjectOwner: group.subjectOwner,
         subjectTime: group.subjectTime,
         pictureUrl: picture.profilePictureUrl,
-        size: group.participants.length,
+        size: group.participants?.length ?? 0,
         creation: group.creation,
         owner: group.owner,
         desc: group.desc,
         descId: group.descId,
         restrict: group.restrict,
         announce: group.announce,
-        participants: group.participants,
+        participants: group.participants ?? [],
         isCommunity: group.isCommunity,
         isCommunityAnnounce: group.isCommunityAnnounce,
         linkedParent: group.linkedParent,
@@ -4941,10 +4941,16 @@ export class BaileysStartupService extends ChannelStartupService {
   }
 
   public async fetchAllGroups(getParticipants: GetParticipant) {
-    const fetch = Object.values(await this?.client?.groupFetchAllParticipating());
+    // groupFetchAllParticipating() can resolve to undefined/null (for example when the Baileys
+    // store is not synced yet right after a reconnection), which made Object.values throw
+    // "Cannot convert undefined or null to object".
+    const allGroups = await this?.client?.groupFetchAllParticipating();
+    const fetch = allGroups ? Object.values(allGroups) : [];
 
     let groups = [];
     for (const group of fetch) {
+      if (!group) continue;
+
       const picture = await this.profilePicture(group.id);
 
       const result = {
@@ -4953,7 +4959,7 @@ export class BaileysStartupService extends ChannelStartupService {
         subjectOwner: group.subjectOwner,
         subjectTime: group.subjectTime,
         pictureUrl: picture?.profilePictureUrl,
-        size: group.participants.length,
+        size: group.participants?.length ?? 0,
         creation: group.creation,
         owner: group.owner,
         desc: group.desc,
@@ -4966,7 +4972,7 @@ export class BaileysStartupService extends ChannelStartupService {
       };
 
       if (getParticipants.getParticipants == 'true') {
-        result['participants'] = group.participants;
+        result['participants'] = group.participants ?? [];
       }
 
       groups = [...groups, result];