Improper or poor use of the grappling hooks can leave you flying across the map in various ways and this issue can cause grappling hooks to attempt to push you into geometry causing you to suffocate.

Easiest way to reproduce this is to place a hook into an object while you're on the ground and trying to 'swing' to the side, you should orbit it on the ground like a May pole.

If you're on the ground, grappling hooks should work much like how leashes/leads work on horses (they're free to wonder around, as long as they don't go beyond the range of the lead).

Mod information:
MCP: 9.05
FML: 8.0.99.99
Minecraft Forge: 11.14.3.1450
grapplemod: 1.0