Hi, sorry if I am mistaken. I've done a little research, but am still pretty new to learning Japanese.
I was learning this morning the kanji 誤 but was confused when the "Write it!" panel looked very different to the kanji displayed in the initial slide. The dictionary (which I thought to screenshot afterwards) also has the same difference between the main kanji display, and the mnemonics and strokes display.
I first searched, trying to work out if it was just a font difference, or if they were different characters; but it appears to be related to unicode rendering and the unicode Han unification.
Some fonts don't show the difference, but those that do switch depending on the language context given.
To understand and demonstrate it, I tested with simple HTML, and it looks like setting lang="ja" should fix it?
Can you try it again now? I just came here because Renshuu was using the wrong font for me. Now suddenly it works again. If you didn't change your font, check now if it switched back to textbook (it should then look like in ポールオジチャン's screenshot.
If it does, then we had the same issue at the same time.
Are you on the app's, or using a browser? There is an issue being looked into with the company that offers that fonts where ublock origin is blocking the requests on renshuu to the font server. Disabling ublock for renshuu fixes the issue (we don't have any ads or tracking cookies or any of that junk, anyways).