Backspace issue

[Totokis]

When I try to write second time, it shows message "Tekst zawiera błędy, bądź użyto backspace'a, proszę spróbować ponownie", even though the backspace was not touched

[arksimatic]

Could you please provide more details on this topic?
Press the button "Show/Hide Results" and some kind of logs will appear, please share them (especially if any of them contains "backspace")