I had similar issue. Tiller handle screw broke off on my 2016 Hobie TI....while sailing offshore....Luck for me the TI has two steering positions. This was with the risers that add extra side loads.
Found hidden corrosion at break point. The broken screw took a bit of work to remove (broke deep into receiving hole).
See photo below.
I have switched back to the stock tiller (no riser / less side loads) and now swap out the tiller handle stainless steel screw (both) on my TI every 1 to 2 years for safety.
I am also moving to 316 stainless for next swap out.
I do sail a lot in coastal conditions (salt water).
I am thinking of adding a simple sacrificial anode plate to the stern to lesson corrosion on the TI (rivets on the AKAs are also taking a hit....).
Hobie TI Tiller Handle Screw Failure by
Jim Powers, on Flickr