This is the expected behavior when using temporally blended effects.
This post talks about why transparent objects and motion blur / temporal blending don’t play nice together.
The short of it is that accurately compensating for motion with TSR and/or motion blur requires accurate depth and velocity buffers. There is only one depth and velocity buffer, so it is only possible for it to be accurate for either the foreground or the background element, and the greater the discrepancy in depth or velocity the worse the artifacts become.