By default, Opera Mini nowadays uses a client-side and modern rendering engine that works fine everywhere. But if you change the "Data saver" setting to "Extreme" (which might be the default if you upgraded Opera Mini from an old version) then Opera Mini uses its arcane server-side rendering engine which hasn't been updated for years (based on Presto, i.e. Opera 12).
That should explain why everything is working fine for most Opera Mini users but not for all. If you have problems then don't use the "Extreme" data saver option.