Yes pandas do eat their own poop.
Pandas and especially the baby or young pandas eat their own poop because the panda poop contains bacteria that the pandas need in their bodies to digest food properly.
Basically pandas especially the baby pandas eat their own poop to obtain the bacteria required to properly digest vegetation found in their habitat and ecosystems.
When pandas are sterile the baby pandas intestines are sterile and do not contain that needed bacteria so they get the bacteria from the poop.
It's not only pandas that eat their own poop but also koalas, and hippos as well as elephants and even dogs eat their own poop.
Eating their poop actually helps their digestive health.