Umm... not to be too argumentative here, but solid thermocouple wire is more the norm than stranded is in many aircraft, particularly certificated aircraft. Ask me how I know... I got really good at silver soldering the alumel/chromel wires in MD500 helicopters many years ago. And it never broke in service.
Fast forward to today and you'll find most of our probes, mounted right there on the exhaust pipe, being heated and shaken by our dinosaur Lycomings are also using solid thermocouple wires. Same for the CHT probes. Solid wire is generally not acceptable for use in aircraft applications but thermocouples seem to be (and to have been for many decades) the exception to that rule.