Thanks for tagging me @ThomasManthey. Yes, I had this issue when I upgraded to 3.15. Then I continued to have this issue when I upgraded to 3.13. You can see my previous post here:
There’s two systems that I setup that have this issue. I troubleshooted it at the time, but since have downgraded the MPPTs to v3.13 on both. Honestly, I gave up on trying to upgrade to newer firmware versions due to no interest or actions from Victron representatives. But let me know if I can help in any way now.