Board Thread:Questions and Answers/@comment-31863149-20170429010806/@comment-31900696-20170502205122

Same here, I've had this issue for quite a while now. Jumping does intermittently work but, even with full Gem Armour equipped (Hurricane Boots on), the jump lags significantly and I will suddenly start to fall as Tekkit stops seening the 'jump' command and then spots it again.

I have noticed it seems to be more prevalent when you walk backwards whilst building (or that may be my imagination), also, Construction Foam seems to make it happen more often. ..

I find that flipping between left click and right click whilst simultaneously trying to move forwards and backwards seems to unstick me - again, that may just be my imagination! (P.S. Before trying this, deselect the Catalytic Lens in your hotbar or large holes, craters and tunnels appear in your map; it quite spoils your view, trust me)!