Weird Noises?

I have been using this app for years to make video edits, and it works really well. Recently, whenever I make a new video, I hear this weird thudding-type sound whenever I adjust the length of a clip or move a different clip in between one that I have split. It is hard to explain if you dont hear it for yourself. It is also really annoying since most of the videos I make, I post onto Instagram and having the viewers just seeing random transitions put in at random times without any warning. I dont know if anyone else has been experiencing this or if this is something that I have done? If it IS something wrong with the app, can you fix it please? I hate having to use transitions when they arent needed.

JendallSchmidt about iMovie, v2.2.3