Niigata 80HN BV Ready alarm

Our Niigata 80 HN gets this :BV Ready" alarm on the operator screen. The drives do not show that they are in alarm and I can't find what is causing it. It will clear after pushing and holding "Cancel" and the letter "P" then pushing the reset but it sometimes takes almost 15 minutes and several attempts before it clears. I was wondering if anyone has experienced this before and maybe has an idea as to where I should be looking to remedy this annoying alarm. Any help would be appreciated. Thank you.