Radial piston engines require proper handling techniques to prevent damage through miss handling.
Radial piston engines are not all alike in reliability...for instance take the P&W 1340 and compare them to the P&W 985 ( Both are relatively small Radials )
The 1340 is no where near as reliable as the 985.
I have never had a 985 quit on me in many thousands of hours flying them in the Stinson Reliant/ Stearman/ Beech 18 wheels and floats/ Anson mark 5/ and the Beaver.