Padma purana 89-90a
“O you descendant of Raghu, O you good one, you have done this mission of the gods. O Rāma of a great vow, take (i.e. choose) whichever boon you like. By your deed this śūdra has physically gone to heaven”
While valmiki ramayana says
"Thou hast protected the interests of the Gods, O Highly Intelligent Prince, now ask a boon, O Beloved Offspring of Raghu, Destroyer of Thy Foes. By thy grace, this Shudra will not be able to attain heaven!”
Hence the question: Did shambuka attain heaven?