In short:
In chat where topic mode in turned on have this type of problems:
When a group reaches one million messages, telegram will delete old messages to optimize the database. It creates a lot of problems with topic mode chats. For example, when you write to one topic, it will duplicate to the main topic chat. I wrote to every possible telegram support, but they are not responding. I know why this problem is appearing. In topic mode, each message answering to message that informs that topic was created. When telegram deleting old messages, it deleted this infor message, and telegram can't find which topic to write and send it to main topic. Please fix it!!!
Full Description for this bug https://bugs.telegram.org/c/33045
In short: In chat where topic mode in turned on have this type of problems: When a group reaches one million messages, telegram will delete old messages to optimize the database. It creates a lot of problems with topic mode chats. For example, when you write to one topic, it will duplicate to the main topic chat. I wrote to every possible telegram support, but they are not responding. I know why this problem is appearing. In topic mode, each message answering to message that informs that topic was created. When telegram deleting old messages, it deleted this infor message, and telegram can't find which topic to write and send it to main topic. Please fix it!!!