Yes, there is. Mods modify the game client. WG is releasing new and new versions of the game client and every new release brings changes, additions and deletions. If something changes in the client that a mod relied on to work, the mod will not work anymore. In most cases the modders will update the broken mods: it may be quick and easy, or it may be difficult, requiring some time, and sometimes it's not even possible.
After a new major release the modders, who are hobbyists, will need some time to fix all what the new release has broken.