I don't know why it would not cut fibre glass.
The manual gives the correct blade speed for cutting Asbestos and bone. They can't be that different
http://www.sharkbandsawblades.co.uk/downloads/metalworking_vertical_bandsaws_handbooks/RWS RWH Early Models Handbook 1E WM.pdf
Section 16
Probably a dust collection issue, like how you shouldn't grind metal on a sander full of wood dust or maybe it just made too much mess.I don't know why it would not cut fibre glass.
The manual gives the correct blade speed for cutting Asbestos and bone. They can't be that different
http://www.sharkbandsawblades.co.uk/downloads/metalworking_vertical_bandsaws_handbooks/RWS RWH Early Models Handbook 1E WM.pdf
Section 16
There is a load more manuals available there for download.Great link, very useful as the main belt does need tensioning.