In T313900 a number of users who were renamed, and due to a bug therefore had an inflated edit count, had their edit counts reduced. This had an unintended consequence - some users no longer have a positive 'recent edit count' in The Wikipedia Library, and therefore they cannot use the library.
The Wikipedia Library tracks every user's edit count over 30 days, to understand whether they have reached the '10 edits in the last 30 days' criterion for access. For some of the users impacted by the above task, their edit count 30 days ago was higher than it is now, resulting in negative edit count.
See example from @jrbs:
{F66025899}
This issue will clear up over time. The scripts were run on September 1st, which should mean that by October 1st this is no longer an issue. It may not be worth us doing anything in the meantime.