Can you give some context here?  It looks like search results, and the results are sorted by name.  It's not specified how results will be ordered within those groups.  You can sort by one of those columns, but of course then they won't first be sorted by name.

It is possible that even though it's not specified that they used to come back in an order that happened to match one of the date column's ordering.  Depending on the kind of search the order may be determined by the way they are returned from the underlying database, which can in turn be influenced by things like the types of indexes you have or the way those indexes are used, which in turn can depend on the size of the tables involved.  So even just the natural growth of your repository can change the observed behavior.

The Web Client allows you to specify multiple sort columns, so you could sort first by name and then secondarily by another column.