Hi @FranHefner, thank you for your patience and tremendous support to help debug this!
We have narrowed the issue and found out that the root cause of the issue is a display side effect.
The governance canister deletes the proposals’ ballots information once, and only once, the proposals’ reward status has settled. It does that to collect certain data to make sure it does not exceed canister memory limits.
As these ballots are the root information to find eligible neurons and per extension display the ineligible neurons, receiving empty ballots makes NNS-dapp UI think and display that all neurons are ineligible.
Therefore, to fix the issue, we will have to amend this empty ballots and renders the information more appropriarly. This still needs to be refined but we will do.
It is worth to note that you found an issue that has always been there, so good catch 
.
When it comes to your concern about your rewards, as the above and root cause isn’t directly related with these, it is most likely all fine.
Let me know if you have more questions and thanks again 