When I add one video to another, snapping the two together, there is a one frame black and jump in sound. MEP 2016 Plus. I have done the update. Win 7 Pro 64.
Try zooming in to 1 frame and then drag the left object to the right. Make sure that you are in multi-track or single-track mouse mode and not regular mouse mode, otherwise you will find another gap further along.
Can you post a screen shot ot the section of the timeline zoomed in where the 'black frame' appears. Note please crop the screen shot to only show the section of timeline before and after the join.
Also check the following:
the black frame is not part of the actual video either at the end or beginning.
In the programs settings, check the option shown below is not set
Another possibility is if the video is from a camera that records to memory card and the 'black frame' is at the boundary of where the camera has reached the max size for a single video file and has started a new one - this can result , in some older cameras, with a half frame missing.
If this is the case then the camera should have come with software which will import the video to your computer and correct the black frame issue.