To be precise where new content is being overlaid, use the buttons (or <Shift>+<Right or Left> shortcuts to have the scrubber (red-line) land at the joint between clips.
Then right-click the new clip in the bin and OVERLAY ON SEQUENCE AT CURSOR. That way, the overlay should be just above the intended clip.
If this doesn't do the job, what version of VP is being used? Upgrade to the latest. For licensed users upgrades are free for up to six months from purchase date. After that, VP will continue to fully function but a fee will be required in order to register the newest. Retain your old install file and registration info.