Contradiction with Luke 24:50-51
This verse states that Jesus blessed the disciples near Bethany and was carried up into heaven, suggesting a singular event, while Acts 1:13 describes the disciples being in the upper room after the ascension, indicating more time between events.
Luke 24:50-51: And he led them out as far as to Bethany, and he lifted up his hands, and blessed them.
Contradiction with Mark 16:14-19
These verses imply that the disciples went out to preach right after Jesus' ascension, whereas Acts 1:13 depicts them as gathered in an upper room.
Mark 16:14-19: Afterward he appeared unto the eleven as they sat at meat, and upbraided them with their unbelief and hardness of heart, because they believed not them which had seen him after he was risen. [at meat: or, together]