bug

Hi, I want to report a bug. There is a supergroup with multiple admins, but I am not an admin here. This group has been a basic (non-super) group until (probably) 7 August 2017. Today I wanted to clear this group’s messages from my phone’s cache (I do not remember why) and pressed and hold on it. “Clear History” option appeared instead of “Clear from Cache”, but I assumed that it will delete messages only from cache because in supergroups' message history is unified and I was not an admin. After selecting 'clear history', all the messages except the last message after 7 August 2017 are deleted for me. I think the problem is from server side because I checked from multiple devices. I left and was added to group but problem still exists. Please investigate this. Can you restore message history for me?