When using Telegram in Samsung One UI's pop-up window mode, resizing the window or switching between pop-up and fullscreen mode sometimes causes Telegram to lose the currently selected forum topic.
Instead of displaying only the messages from the selected topic, Telegram suddenly shows messages from multiple topics mixed together, including pinned messages belonging to different topics.
The message input field remains functional, but any new messages are sent to the General topic instead of the previously selected topic. This is particularly problematic because users may accidentally send messages to the wrong conversation without realizing it.
Additionally, pressing Back from this broken state returns directly to Telegram's main chat list rather than the supergroup's topic list. To recover, I have to reopen the supergroup and manually select the correct topic.
Expected behavior: Telegram should preserve the selected topic, its messages, pinned messages, and message destination when resizing or restoring the window.
This issue occurs intermittently and has also been observed in Telegram Beta and Plus Messenger.
Steps to reproduce
Open Telegram on a Samsung device using One UI's pop-up window mode.
Open a supergroup with forum topics enabled.
Enter any topic other than General.
Send a message or simply stay inside that topic.
Resize the Telegram window or switch between pop-up window and fullscreen mode.
Repeat resizing if necessary, as the issue occurs intermittently.
Telegram unexpectedly displays messages from multiple topics together, including pinned messages from different topics.
Try sending a message. It will be posted to the General topic instead of the previously selected topic.
Press Back. Telegram returns directly to the main chat list instead of the supergroup's topic list.
Reopen the supergroup and select the original topic to restore normal behavior.
The issue occurs every single time the window is resized or switched between pop-up and fullscreen mode while viewing a forum topic.