I can't find a way to modify the mode of a structure block, other than right clicking on it and changing it through the GUI.

When you use commands to update the "mode" NBT tag, the block remains in "load" mode. If you right click on the structure block after modifying it's mode tag via commands, the texture of the block will update to whatever you changed it to, but the GUI will still open in "load" mode. after clicking done, the structure block's texture will update properly (back to "load" mode, or whatever mode that was selected when you clicked done).

I tried using the setblock command, and the data command. The exact same results happen when using the debug stick.

If anyone knows a way to set a structure block's mode without using the GUI (preferably using commands) please let me know. Otherwise, this seems like a bug to me.