Not sure what is going on there. The caching of OptiX and CUDA programs shouldn’t match for PTX from different OptiX versions, esp. not if the assembly of the mismatching functions has changed. That sounds more like some issue with the build environment not updating to the correct include folder when switching OptiX SDK versions.
I’m handling that with CMake and custom build rules for the *.cu files in my examples and haven’t seen that happening when changing the OptiX versions. That’s effectively a “rebuild solution” step anyway.
That is handled inside the CMakeLists.txt and *.cmake files of these examples: https://forums.developer.nvidia.com/t/optix-advanced-samples-on-github/48410/4
You should be able to see if programs have been found inside the cache from previous runs, although they shouldn’t, by deleting the cached data, running with new and then old PTX code, and having the OptixDeviceContextOptions log callback running at maximum level 4 as well.
https://raytracing-docs.nvidia.com/optix7/guide/index.html#context#compilation-caching