Sharepoint 2013 has double encoding issues where spaces in URL show up as %2520. I understand what this means. = %20 on first encode, then <%> = %25 on second encode, so I end up with %2520. I do not know how to stop the double encoding from occurring. This was not upgraded from another previous edition or migrated, this event just randomly started around two weeks ago. Do you guys have any thoughts?
This is a very old bug, from a 2014 Cumulative Update if I recall. Install a newer CU, such as the March or April 2016 which appear to be fairly stable.
EDIT: It was from April 2014/MS14-022: https://thesharepointfarm.com/2014/06/workaround-ms14-022-double-encoding-bug/. Resolved with the September 2014 CU.