You need to break that apart and see if there is any bark or dirt in it. That's one of the reasons why the Forum recommends NOT using substrate. Definitely not normal. Keep an eye on his poo schedule from here on out to make sure he doesn't get that constipated again.
What have been feed him lately and how are your Temps been? They nend heat to help digestion too cool and metabolism slows they will take longer to poo and it will back up and when they do it will be bigger poo. Also a lot of meal worms can cause this it is harder for them to digest.
And, to help prevent him from swallowing substrate he picks up on his tongue, you could lay a piece of window screen on the surface. Watch your cage humidity and make sure he's drinking enough. Constipation is a sign of dehydration.
I would definitely note dehydration. His urate has a yellowish orange tinge to it. Also, the substrate could have played a role in constipation, as the stringy part looks like partially undigested plant matter/bark. If the substrate is necessary for whatever reason, try a layer of mesh over it.