I have spent numerous hours on this issue. You can read my last post here...( https://sundance-communications.com...1339/re-sbx-mailbox-wont-open#Post611339 ). I eventually had to replace all 3 sites. I recently spoke with Toni at Vertical and she said they had a bad run of cards (Mine were all installed in Late 2016 and probably made early to mid 2016). The ONLY fix is to replace the card. The problem is that "some" of the cards that Vertical was using to replace them were experiencing the same issue and that they were working with the manufacturer on a solution. Your best option will be to get with Vertical and see if they will replace it under warranty. BTW, none of the sites are experiencing the issue once I replaced the card and it has been over a year for 2 of them. Good luck!

"I thought I was wrong once, but I was mistaken"