Workaround : Right-Click on the AkEvent notify on your animation ---> Open Notify Blueprint ---> Delete the exec node going into print string (works 100%)
I was having this error for ages, couldn't figure out why! Apparently, if I uncheck the follow button on the details tab of the notify the error stops - but then it posts event at location instead of mesh which is a bummer. If you look through carefully in the blueprint there is a 'Print String' node for the true condition of 'Follow' and then it posts the print string of the error. I haven't solved how to actually stop the error. But the workaround just works fine. I just ended up deleting the exec node to print string and error has stopped. The sounds work fine so I don't care - although I'd be interested in knowing what the actual issue is and if Audiokinetic is addressing it in future updates!
From the true exec node of Branch after Get AK Component, going into the Print String - just delete it!