You might have switched to another style that has a different denominator during MIDI recording. For example, if you switch from a style in a 4/4 time signature (Beat) to a style in a 6/8 time signature during MIDI recording, the style in the 6/8 time signature will be played back at an incorrect tempo when the recorded song is played.
If you want to record a song switching multiple styles with such time signature combinations, then it is recommended to record a song in audio format rather than in MIDI format.
NOTE: You can’t change the beat while a style is playing back or a MIDI song is being recorded/playing back.