My information is that ..."in 1938, a 500-lb. chunk of one of the gargoyles fell off, tearing a hole in the roof and landing in the attic. Soon after that, all four gargoyles were removed in the interest of public safety.
Replica gargoyles were installed in 2002."
This info from: http://www.traditionalproductreports.com/roofing-copper.html
View attachment 191947
I think the gargoyle drop was in 1921:
A gargoyle is removed from City Hall after dropping its jaw through the city hall roof. Photo of the gargoyle being installed 20 years ago. Head weighs 500 lbs. Jaw dropped 100 ft through the attic and almost killed a city hall worker in the Works Department draughting room. The city architect wants the dozens of gargoyles to be removed now. It was the gargoyle at the NE corner of the tower which fell yesterday. This gargoyle made of New Brunswick sandstone. These seem to be crumbling in the city air. This gargoyle was 250 ft above ground level, one of 4 around the tower (Toronto Star 9 Mar 1921 p. 1).
The Property Commissioner reports that repairs to the stonework are proceeding. The stonework on the gargoyles was very defective and the stone needs to be removed. Recommended for urgent removal by the City Architect and the stone masons consulted. Scott Bros., stone masons reports that the gargoyle on the SW corner is in fair condition, the others on the other corners are in poor shape. Head, neck, paws of gargoyles to be cut away. George Oakley & Son stonemasons finds the gargoyles dangerous, weather worn and liable to fall at any time, danger of loose pieces falling (Toronto City Council Minutes 1921 Appendix A Property #7 8 Apr 1921 p. 530-531).
The city hall gargoyles are in dangerous condition and are to be cut away. Heads and necks are to go, and perhaps the rest (Toronto Star 8 Apr 1921 p. 14).