Ok - I have changed back to the default skin and its ok. As this is a new feature it looks like the skin I am using will need to be updated. If an admin can delete this thread please do.
I can delete it if you really want, but this seems like potentially useful information that someone else might come across wondering why they too get an unhandled exception when they delete.
server: NextPVR 5.0.7/Win10 2004/64-bit/AMD A6-7400k/hvr-2250 & hvr-1250/Winegard Flatwave antenna/Schedules Direct main client: NextPVR 5.0.7 Desktop Client; LG 50UH5500 WebOS 3.0 TV