Rekordbox is changing my bpm mid song

I am going to try to explain this as well as possible. I am not sure if this is just a setting I need to change but rekordbox changes the bpm mid song with a few of my tracks. For example, The Champagne bop by Dr. P. Track is 140 BPM but there is a section of the song where the bpm will drop down to 103 and then later in the track go back to 140. How do I make it to where the BPM is not fluctuating throughout the song?