I've encountered an issue with missing content in the Rewards section of the Mojoverse Arena. So after you've battled 3 champions, you go to the rewards of that series (battlechips and gold). There are two buttons present (next serie - continue) Instead of using those I use the top menu to go to the homescreen (and collect the rewards of the solo objectives). Going back to the Arena select screen I see a Continue button on the Mojoverse Arena. Clicking on that button shows the following screen:

Using the described steps will always show this missing content screen.
Further information:
Sony Xperia XZ2 Compact, with Android 10, on WiFi
Game version 25.3.0