I'm typing '2015/16 Media Kit' Indesign automatically changes it to '16/2015' in the textbox
Do you have the Autocorrect preference turned? Are you running any third-party software which expands text like Text Expander?
Just checked and no autocorrect is not on ... no 3rd party either
All I can think of is to restore your InDesign preferences:
Trash, Replace, Reset, or Restore the application Preferences
Retrieving data ...