Files get stuck in ”Waiting to upload”

I am using iCloud drive (upgrated to 200GB) and it works perfectly with macOS devices and my iPad. But with my iPhone SE files get stuck ”Waiting to upload” status when trying to send a new copy or edited file to iCloud. Downloading works with iPhone. There is plenty of free space available and everything works with my other devices. I have tried to switch off and on then iCloud setting with my iPhone and also signed out/in with my Apple ID, still the same problem sticks. I think this has been on already several months and I would hope to get it fixed. iOs version is up to date 11.4.