Hardware acceleration can be an issue for video editors. What is involved is a) a driver which uses a companion special purpose cpu that speeds up the processing, rather than relying on programming a normal x86 unit (the video editor - PD18 - makes calls to the driver to do the render processing in accelerated mode). This video cpu may be on a display adapter if you use one, or as part of the x86 processor chip powering your PC; b) the system hardware itself, and c) software compatibility between these and the editor itself.
Problems with the various parts of acceleration can manifest in different ways.
If you are using a display adapter, the driver for that may be the cause of your problem: ensure that it is up-to-date.
Often, simply trying to render in accelerated mode gives error messages. In my case, I run an intel core i3 processor that Intel claims to have a video cpu on-chip. However 2 video editors (PD18 and Video Studio 20201) that I use both generate errors when attempting to render 'with acceleration', and both work normally when not accelerated. They both could not be wrong and after an extensive interchange with Intel, it seems that the driver for my graphics chipset (which both editors use in acclerated mode) has an issue using the special video cpu, and Intel won't be updating it. Which led me to the following.
You remark that the un-accelerated is smooth. If you cannot identify a cause of the jerky rendered result, then possibly you will have to workaround it. For example; use small duration projects (up to say 15 minues) with un-accelerated rendering. This way, the extra time to render (compared to a nominal accelerated process) will not be very obvious. For me at least, this wasn't a big issue - I never work with large projects (say, 40-60 minutes each) because changing anything in composing the project file gets tedious when they are that large.