Sorry about the trouble. It indeed is a bug.
To get out of the situation, you need to create a "TV Channels" smart list, and fix thing from there.
To create a TV Channels smart list, in Standard View, press F9 to bring up "Add Smartlist" dialog. Set the name to your liking, under Rules, set "Media Type" "is" "TV".
To fix channel grouping problem, go to the TV channels smartlist. Find the offending channel, right-click, Stacks > Unstack.
Alternatively, you can fix all problems by selecting all channels in the smartlist, and right-click, Stacks > Advanced > Error Check and Correct Stacks. You will get a report in an opened text file, in which you may find entries like this:
Clearing bad top (7-3 E1_4 WL)
After doing the above, you should be able to go back to TV Options and regroup your channels. Since the ordering tool is broken, you need to make sure you first select the channel that you want to be on the top of the list, then click Add/Remove to add more channels.