Drag and drop from explorer just works one time to premiere

Try resetting the preferences:
https://community.adobe.com/t5/Premiere-Pro/FAQ-How-to-reset-trash-preferences-in-Premiere-Pro/td-p/8236158

If that doesn't work, try resetting the Workspaces:
Reset a workspace
Reset the current workspace to return to its original, saved layout of panels.
1. Do one of the following:
• Click the Workspace menu icon and select Reset to Saved Layout.
• Choose Window > Workspace > Reset to Saved Layout.
from here:
https://helpx.adobe.com/premiere-pro/using/workspaces.html

If that doesn’t work, try updating or rolling back your graphics driver directly from the video card manufacturer’s site.

Gibbe,

This is not good technique as your A1 and V1 patch panels very often won't work on the second round. Import all your files into the Project panel first. When dragging from there, make sure all 4 blue boxes for A1 and V1 are enabled. Then your clips can be inserted or overwrote correctly into the Timeline.

The developers intention, and editors historically is to to organize clips prior to placing them into the Timeline. If you want a different behavior, make a feature request here.

Thanks,
Kevin