Yeah - it's not unheard of (even on prop planes) for models to break in the air when a canopy is lost.

AFAIK, the most common cause is that if there isn't some kind of blanking plate (or other 'obstruction') at the front end of the upper turtledeck, then a strong & sudden airflow into this area will literally blow the aircraft up from the inside out - you're basically over-inflating it The problem is further exacerbated by models that have sharp edges at the rear of the canopy opening, which acts as a stress focus point.