I moved from 5.31 to 5.32 recently. I noticed that the project setting "Operating system" where you can select "None" or "RTX Kernel" was set to "None" in my projects. When setting them back to "RTX Kernel" and pressing "OK" the setting would not be saved. All projects I open in 5.32 has this same behavior.
I moved back to 5.31 and the setting now works as it should again.
Any idea ?
EDIT: Tried also 5.33, same behavior as 5.32 !
I have seen this when moving between MDK versions. It appears that the newer ones interpret something in the projects by older MDK as it should be using RTX and set the project to use RTX Kernel. It needs to get fixed in Keil MDK -ARM but fortunately easy to deal with once you understand where it came from. It will likely complain about an unnecessary header file being included.