Was the 1992 Gimli DHC-4 Caribou accident ever investigated?
It was, but from what I can tell the report has not been digitized yet.

The gust locks were left installed. The aircraft was being operated in the restricted category as they were retrofitting with the PT-6’s. 

Here’s an analysis from James Donnelly, Bombardier Aerospace. Starts on page 7.

http://www.asasi.org/papers/2001/Four%20Unrelated%20Accidents.pdf

Essentially the rigging was done incorrectly. The gust locks did reduce engine thrust, but didn’t kill it completely. Takeoff roll was 20% longer than calculated.