Voiceover sounds very quiet in the first few seconds then gets back to normal volume

when playing video in timeline premier pro, i have a voiceover and a video with sound on top, the voiceover statred playing at normal gain at first, but when it reaches the part when the video with sound plays on, the voiceover gets quiet, it's like premier pro automatically does that, how do i remove it, there is no visible effects or audio gain change or anything, even when i export it it sounds like that, please help me