There is no sparging or lautering in a typical BIAB process.
A stuck sparge in a traditional brewing process is when the solids (grain/hops, etc.) clog the valve so you can't separate the wort from the grain.
In BIAB, the bag separates the majority of the wort from the grain from the start, and you squeeze the rest of the absorbed wort out of the grain. Unless you are doing something wrong, the grain would never have the oppertunity to clog up the kettle's output valve, so you can't get that flow "stuck."
I do a ton of BIAB weizens (Hefe's)...let me know if you have any specific questions on your recipe or process!
Primary #1 - Midnight Ryeder (Midnight Wheat and Rye)
Primary #2 - Florida Weiss
Primary #3 - Kane-DOH APA (Honey Citra APA)
Secondary #1 - Downtown Flanders Brown (brewed August 2012)
Keg #1 - Raspberry Florida Weiss
Keg #2 - Cinnamon Raisin Cider
Keg #3 - NONE!
Bottled - NONE!