Hi Paul,
Sorry for not provide the system info, the OS is ubuntu 16.04 and afni version is Version AFNI_20.1.07. I just updated afni last month, and the weirdest thing is all the other short cut like ctrl+R or alt+r could work, except the ctrl+r. I can save images in a different way by tapping shift+r, meaning that turn on the recording mode first, and save the current screen shot image next. Thanks for your advice.
-Jack