We did this recently:

Due to sunlight and rain, the 3D model is bad in the main outdoor area.

Id you look further, you will understand the problem is my umbrella above the camera (that was sometimes spotted by the camera itself and puddles that was reflecting sunlight creating "holes".

Question is, is it better to:
1) scan again all outdoor area, THEN delete the old scans
2) delete the old scans, THEN delete the old scans

Problem with 2) is "link" between floors ... will I be able to re-link scans if I delete all scans IN THE MIDDLE before starting ?