I have experienced something similar. One day shrimp just merrily grazing on a sponge filter and fell off lifeless to the substrate . I thought I’m witnessing a shrimp dying breath! 3 seconds later it went spastic and left an exoskeleton and shrimping away.. the tense moment from aw shhh.. to owhh…
Bubbly_Tangelo2085 
sounds like he might be stuck in his molt…
I have experienced something similar. One day shrimp just merrily grazing on a sponge filter and fell off lifeless to the substrate . I thought I’m witnessing a shrimp dying breath! 3 seconds later it went spastic and left an exoskeleton and shrimping away.. the tense moment from aw shhh.. to owhh…
Only when they’re dead….
Apologies for the grammy on my phone and dont have auto correct.