Background Image not updating for Bot

[C4T4]

Checklist

• [x] I am reporting an issue in existing functionality that does not work as intended
• [x] I've searched for existing GitHub issues

Description

I created a bot with BotFather, the bot is working but when I change the background image on iOS it's not updating the picture in the chat with the bot. for other chats it works.

Expected Behavior

should update background

Actual Behavior

not updating background

Steps to Reproduce

1. create a bot
2. start a chat with the bot
3. change the background