I know this thread is old, but I’m still running into this problem when saving taxonomies on the front end as well. As noted it seems to happen when using the acf/save_post function to redirect users during a multi-steps post creation process. That seems to be the common denominator at least.
It can indeed be worked around via the part of the function above, but it would be great if anyone on here had any insight into why the taxonomies aren’t saved as they should be based on the ACF settings and if there is a better method of using acf/save_post that will allow ACF to do its magic alongside it.
