Have seen no reports of inconsistent behavior.
An easy and accurate way to insert is to position the cursor at the split point where the new material is to be dropped, right-click the new clip in the bin and PLACE ON SEQUENCE AT CURSOR. That should do what you want. To snap the cursor to the split, use the ||< and >|| keys under the preview window.
If a new clip is dragged atop another it will replace it.
If an existing clip is dragged on the timeline it will land at the drop point (let go of the mouse button), splitting the original clip.
Each time VP is installed it may exhibit slightly different behaviors. If snapping when a clip is dragged to the right is annoying, try holding the <alt> key.
Or simply reinstall Videopad until clips don't snap back. This may take several installs, but they're very quick. No need to re-download.
When you make a mistake immediately press <ctrl-Z> (EDIT | UNDO) to backtrack step-by-step. Save Project AS routinely, giving it a unique # or name, so as to not overwrite prior saves. Save Project (no AS) will overwrite.