I added one more piece of code to hopefully fix the challenge issue. It will not go up until tomorrow, though.
Challenges update. 2022-03-27 Sun: 10 challenges ︙ (normal) 2022-03-29 Tue: ??? break day 2022-03-30 Wed: 6 challenges and "studied 30% of the last 30 days" ︙ (normal) 2022-04-02 Sat: 4 challenges and "studied 20% of the last 30 days" ︙ (normal) 2022-04-24 Sun: 4 challenges and "studied 0% of the last 30 days," but it's been on 0% for a while with no issue
I fixed the typo. As to the extra challenges, I'm honestly still not sure what is going on with that. I added a bit of extra logging that might help, so do let me me know the next time it happens again.
1. The highlighting of the example sentences is a bit off from the construction/grammar. I put a yellow line in the screencap below to illustrate this. Maybe it was purposefully done to highlight according to the translated sentences?
2. The other places that I'm looking have (なの), parentheses intentional, available as well as の.
From page 286 of the Handbook, the constructions are:
It's also tangled with the usual piecewise alternatives like ではない to じゃない and の to ん, but I don't know enough yet to say if the other versions are strongly related enough for it to matter since this is related to indirectness.
--- edits (multiple edits resorted for readability)
Here are the related grammar pages I found in the Handbook
ではないだろうか (heading 4) on page 235. Doesn't include (なの)
ではないだろうか on pages 286-287. Includes (なの)
ではあるまいか on pages 280-281. Includes (なの)
ではあるまいか on pages 574-575. Includes (なの)
じゃないだろうか on pages 154-155. Includes (なん)
んじゃないだろうか on pages 702-703. Includes (なん)
ではなかろうか on pages 287-288. Includes (なの)
I'd link up any renshuu pages on the above, but I'm not far enough in the spreadsheet yet.
1. Fixed the coloring on じゃない. The ん/の in the example sentences are coincidental, but are not necessary in the construction. I'm not sure that adding them to the construction panel will be beneficial, so I'll add a short note instead.
2. Indeed - that might be a lesson that existed long ago, but for some reason the contents got ripped out. I'll remove it.
3. Generally speaking with the highlighting, I try to highlight enough of it in order to capture the meaning in the linked English translation. That being said, my goal is to highlight the least amount possible. In the example you gave, I could potentially mark as green the entire "Sentence", but I feel like that would dilute the highlighting of the grammar meaning.