Whenever this happened, all those buttons related to the arenas do not work. They either just vanished when you clicked on it, or let you in but the page becomes empty.
It seems the system won't record anything when this issue occurs. Here is an example.
I won a game in Champion and gained 155 coins, so my coins reached 69,679. But, when I login again, my coins only remain 69,524.
https://imgur.com/a/NengKSghttps://imgur.com/a/ZGLzT8hButtons vanished
https://imgur.com/a/uNclDg2Empty design page
https://imgur.com/a/iuVVNyrRecord begin PvE 10150-76169, coins 69,254
https://imgur.com/a/MYiesGPPvE 10151-76195, coins 68,756 (The issue occurred, and I intentionally lost several games in Demigod mode.)
https://imgur.com/a/HW8hhsTPvE 10152-76169, coins 69,711 (Refresh the page, login again, and won two games in Champion.)
https://imgur.com/a/moo3hzK