When i edit videos with Camtasia 2018 there's a little audio retard while i'm editing and whenthe video is exported. Why This?
Were the clips recorded with Camtasia or did you bring them in from elsewhere? If the clips were recorded as variable bit rate (search VBR) that's the typical reason for A/V going out of sync. Programs such as Handbrake can convert your clips to CBR (constant bit rate) rather easily.
I have been having the same issue with video recorded with Camtasia Recorder 2018. The audio delay is very small, but just enough to be noticeable and annoying to me. I tried all the solutions here (https://feedback.techsmith.com/techsmith/topics/audio-out-of-sync-in-2018-version) and none of them worked.