Hi,
I'm running Windows 10 Home, and I don't know when this issue actually started, but I just started trying to figure it out last weekend. Explorer.exe uses 12-15% CPU and keeps my processor at max frequency. When I look in Process Explorer, this is the stack trace for the problematic thread:
Thread: ntdll.dll!TppWorkerThread
Stack:
wpncore.dll!TileQueueManager::RequestToastNotificationWithPrivilege+0x260
wpncore.dll!TileQueueManager::RequestAllToastNotifications+0x82
wpncore.dll!ToastRequestNotificationWork::Invoke+0x5f
wpncore.dll!ThreadPool::ThreadPoolProc+0x1f5
ntdll.dll!TppWorkpExecuteCallback+0x35a
ntdll.dll!TppWorkerThread+0x6da
KERNEL32.DLL!BaseThreadInitThunk+0x22
ntdll.dll!RtlUserThreadStart+0x34
I grabbed a screenshot of the process details in Process Explorer (it says ntdll.dll!EtwEventRegister at the top instead of nppdll.dll!TppWorkerThread because I hadn't configured symbols properly yet). If I kill TppWorkerThread, overall CPU usage drops to 2-3% when idle and my CPU isn't stuck at max frequency anymore. Unfortunately, it comes back eventually (probably within 30-60 minutes) or if I restart my computer. Also might be worth mentioning that this also happens when I boot into safe mode.
I also noticed that I'm unable to load the "Notifications & actions" Windows settings -- it just sits there with the loading dots moving across the window forever. I would assume it's related to whatever problem is happening with RequestToastNotificationWithPrivilege... but I've also gotten toast notifications from a couple of applications (Adobe Reader, at least).
I ran the Tweaking.com repair tool overnight last night, but unfortunately it didn't clear up this issue. I was hoping to be able to avoid doing a Windows refresh, but if there's nothing else to be done then that's what I'll do.
Thanks for any help you're able to give.