Well, first it was in an upside-down tank, then it moved to a sideways tank. So that could be the problem... J/K. :)
Assuming you have good water parameters, all leathers do this as they acclimate to a new environment. Some leathers can take a few days, while some could even take weeks. My long tentacle toadstool took almost two months to fully extend polyps.
During this time they do random things like shed skin, extend polyps briefly, or extend polyps only from certain parts of their crown.
As long as the flesh itself does not appear to be disintegrating or melting away, then it would be safe to assume that the coral is still trying to get used to the new tank.
It also looks like your coral is some form of sinularia. That genus requires some calcium more so than other soft corals.