I'm a group manager bot creator and I realized that some users have found a bug in telegram, they put some specific characters in their message, when that message is sent, no update is sent to bot api webhook, until another message is sent to the group, when another message is sent to the group that message in question is also sent to webhook. this causes the message to remain in the group for hours. you can find a sample of it here: https://t.me/khsdfkjshdfsdfsdf/119
1- put that dummy chars in a message.
2- send the message to a group that has a bot in it.
3- the message will not be sent to the bot webhook until another message is sent to the group.