I drew a text frame and turned on the auto sizing to horizontal and vertical with no line breaks. I began typing and things are not working as planned, no matter which reference point I use for sizing. This happens with more than 2 lines in a text frame. As you type in the text frame, you can see the box jump to a wider size and then get smaller and then large again.
I am using ID 17.4x64 on a Dell Precision 5570 with Windows 10.