[Skullcatrons]

Wherever you click on a skill that popped into chat-box, it wipes the entire chat history right there and present you new entry screen as well giving you description of the skill.

Reproduction:

Simply click on any skills used in combat.

It will wipe the chat-log.

[Neus]

I can't replicate this.

Was this during or after you participating in an event, possibly with skills that had special styling?

[Skullcatrons]

After testing. It is most likely possible related to eventmins' renaming skills to their own brand that could wipe chat. So yes.

[WaifuApple]

Can confirm, happening to me in an eventmin fight with the text of a monster skill flavoured to be red.

[AkaInuHime]

I've had it happen in event fights even with clicking the names of my own skills in the chat log, not just renamed ones