Question: Could someone please explain "band erosion" and "band migration" a bit more specifically. Thanks!

Some Posted Articles addressing this question:

Band Erosion: Incidence, Etiology, Management and Outcome after Banded Vertical Gastric Bypass (By Dr Fobi, etal)

Interesting to notice that the incidence is quoted as being less than 1% of the time in all surgeries mentioned.

Weight Loss Surgery AGB (Dr. Göran Hellers, Stockholm, Sweden)

Eastern Surgical (Australia) [Complications Report]
Band erosion - Rare, less than 0.5%. Requires another operation, usually a 
large incision. 

NYU Medical Center's Program for Surgical Weight Loss [Report]
Band Erosion: There is a rare chance that the band can erode into the stomach.   This does not cause pain, but may result in inadequate weight loss. This is  diagnosed by endoscope and would require surgical repair laproscopically.   For this reason, aspirin and ibuprofen should be avoided. 

and of course,

The BioEnterics Risk Report

The BioEnterics Patient Booklet