We have been experiencing the same issue with domain sync for several months now.
Considering how many users were experiencing issues, and how old the thread is, It's pretty frustrating to see the lack of response from WHMCS. This thread is over a year old and it has two pages of users having the exact same problem with zero response from WHMCS. Everyone mentioned that they were either experiencing similar issues, sending in tickets with no responses, or that they would follow the thread.
Why do companies even have forums if they aren't going to engage with their audience and actually engage with their audience to address their needs.
Is this the level of support I am to expect with WHMCS?