Okay, I've taken a few screenshots that can hopefully show this better. Here's the first one, showing the topic splitting UI, with the unlabeled set dropdown menu outlined in blue.
If I try to click the Save button on this as is, the page loads for a second, but then just shows this exact same screen again, and the topic is not split. The reason for this only becomes clear when you click on that dropdown menu and select a set. See below:
As you can see here, it seems that if a set has a required field, as this one does, the software doesn't allow me to split without first selecting the set and filling out the required fields. This happens even if I'm splitting a topic in a forum that has no sets assigned to it.
I hope this explained the issue a little better. Any ideas on how to solve this?
Thanks!