I have re-glued that velcro with plastic glue in disconnected areas. I've often thought of using PVC glue which seems potent and instantaneous. The main thing I wanted to say was one work around solution I found when attaching velcro by any means is to use short length pieces (~2 inch) with a gap (~1/8 inch) between them which compensates for the expansion difference of the velcro versus the material (e.g., metal) being attached to.
AL