I have had this happen to me twice. After rain started the main strategy tool accessed from the top of the viewer did not apply the tire I selected. Instead the default tire from the strategy tool by the driver was selected. I chose inters from the main strat screen and SS were put on my car. I then stopped again but used the strategy tab by the driver to change to inters and that was successful at getting the right tire but then the game tried to pit my car every lap until the rain stopped and I put on dry tires.
In another race today I responded to rain by selecting inters with the Strategy tab at the top but had SS put on the car. After I fixed that using the tab by the driver and was distracted by pitting the other driver the game pitted the car with inters and applied SS again. It was still raining. This was on my other account (Dee Oldham) @ US GrandPrix. Another player also reported the same problem.