diff --git a/td/telegram/MessagesManager.cpp b/td/telegram/MessagesManager.cpp
index b752f8d5..baabe97a 100644
--- a/td/telegram/MessagesManager.cpp
+++ b/td/telegram/MessagesManager.cpp
@@ -5512,7 +5512,7 @@ void MessagesManager::add_pending_channel_update(DialogId dialog_id, tl_object_p
 
   if (d == nullptr || pts_count > 0) {
     process_channel_update(std::move(update));
-    CHECK(!running_get_channel_difference(dialog_id));
+    CHECK(!running_get_channel_difference(dialog_id)) << '"' << active_get_channel_differencies_[dialog_id] << '"';
   } else {
     LOG_IF(INFO, update->get_id() != dummyUpdate::ID)
         << "Skip useless channel update from " << source << ": " << to_string(update);
@@ -22967,7 +22967,7 @@ void MessagesManager::get_channel_difference(DialogId dialog_id, int32 pts, bool
 void MessagesManager::do_get_channel_difference(DialogId dialog_id, int32 pts, bool force,
                                                 tl_object_ptr<telegram_api::InputChannel> &&input_channel,
                                                 const char *source) {
-  auto inserted = active_get_channel_differencies_.insert(dialog_id);
+  auto inserted = active_get_channel_differencies_.emplace(dialog_id, source);
   if (!inserted.second) {
     LOG(INFO) << "Skip running channels.getDifference for " << dialog_id << " from " << source
               << " because it has already been run";
@@ -23019,7 +23019,7 @@ void MessagesManager::process_get_channel_difference_updates(
       }
     }
   }
-  CHECK(!running_get_channel_difference(dialog_id));
+  CHECK(!running_get_channel_difference(dialog_id)) << '"' << active_get_channel_differencies_[dialog_id] << '"';
 }
 
 void MessagesManager::on_get_channel_dialog(DialogId dialog_id, MessageId last_message_id,
@@ -23261,7 +23261,7 @@ void MessagesManager::on_get_channel_difference(
 }
 
 void MessagesManager::after_get_channel_difference(DialogId dialog_id, bool success) {
-  CHECK(!running_get_channel_difference(dialog_id));
+  CHECK(!running_get_channel_difference(dialog_id)) << '"' << active_get_channel_differencies_[dialog_id] << '"';
 
   auto logevent_it = get_channel_difference_to_logevent_id_.find(dialog_id);
   if (logevent_it != get_channel_difference_to_logevent_id_.end()) {
diff --git a/td/telegram/MessagesManager.h b/td/telegram/MessagesManager.h
index 97775c2b..ab860f7d 100644
--- a/td/telegram/MessagesManager.h
+++ b/td/telegram/MessagesManager.h
@@ -2584,7 +2584,7 @@ class MessagesManager : public Actor {
   MultiPromiseActor load_dialog_list_multipromise_;  // should be defined before pending_on_get_dialogs_
   Timeout preload_dialog_list_timeout_;
 
-  std::unordered_set<DialogId, DialogIdHash> active_get_channel_differencies_;
+  std::unordered_map<DialogId, string, DialogIdHash> active_get_channel_differencies_;
   std::unordered_map<DialogId, uint64, DialogIdHash> get_channel_difference_to_logevent_id_;
 
   MultiTimeout channel_get_difference_timeout_;
diff --git a/td/telegram/StickersManager.hpp b/td/telegram/StickersManager.hpp
index 598c356c..2b329e61 100644
--- a/td/telegram/StickersManager.hpp
+++ b/td/telegram/StickersManager.hpp
@@ -59,7 +59,7 @@ FileId StickersManager::parse_sticker(bool in_sticker_set, T &parser) {
   PARSE_FLAG(has_sticker_set_access_hash);
   PARSE_FLAG(in_sticker_set_stored);
   END_PARSE_FLAGS();
-  CHECK(in_sticker_set_stored == in_sticker_set);
+  CHECK(in_sticker_set_stored == in_sticker_set) << in_sticker_set << " " << in_sticker_set_stored;
   if (!in_sticker_set) {
     parse(sticker->set_id, parser);
     if (has_sticker_set_access_hash) {
diff --git a/td/telegram/files/FileManager.cpp b/td/telegram/files/FileManager.cpp
index 7204dbff..2a404d66 100644
--- a/td/telegram/files/FileManager.cpp
+++ b/td/telegram/files/FileManager.cpp
@@ -996,7 +996,8 @@ Result<FileId> FileManager::merge(FileId x_file_id, FileId y_file_id, bool no_sy
   bool send_updates_flag = false;
   for (auto file_id : other_node->file_ids_) {
     auto file_id_info = get_file_id_info(file_id);
-    CHECK(file_id_info->node_id_ == node_ids[other_node_i]);
+    CHECK(file_id_info->node_id_ == node_ids[other_node_i])
+        << node_ids[node_i] << " " << node_ids[other_node_i] << " " << file_id << " " << file_id_info->node_id_;
     file_id_info->node_id_ = node_ids[node_i];
     send_updates_flag |= file_id_info->send_updates_flag_;
   }
diff --git a/td/telegram/files/PartsManager.cpp b/td/telegram/files/PartsManager.cpp
index 289983ee..04e10da6 100644
--- a/td/telegram/files/PartsManager.cpp
+++ b/td/telegram/files/PartsManager.cpp
@@ -72,7 +72,8 @@ Status PartsManager::init(int64 size, bool is_size_final, size_t part_size, cons
   }
   CHECK(1 <= size_) << tag("size_", size_);
   CHECK(!use_part_count_limit || (size_ + part_size_ - 1) / part_size_ <= MAX_PART_COUNT)
-      << tag("size_", size_) << tag("part_size_", part_size_);
+      << tag("size_", size_) << tag("is_size_final", is_size_final) << tag("part_size_", part_size_)
+      << tag("ready_parts", ready_parts.size());
   part_count_ = static_cast<int>((size + part_size_ - 1) / part_size_);
 
   init_common(ready_parts);
@@ -157,7 +158,8 @@ void PartsManager::set_known_prefix(size_t size, bool is_ready) {
   } else {
     part_count_ = static_cast<int>(size / part_size_);
   }
-  CHECK(static_cast<size_t>(part_count_) >= part_status_.size());
+  CHECK(static_cast<size_t>(part_count_) >= part_status_.size())
+      << size << " " << is_ready << " " << part_count_ << " " << part_size_ << " " << part_status_.size();
   part_status_.resize(part_count_);
 }