VR effects don't work on stereoscopic videos with a resolution of more than 7250*7250px

Hi everyone,
we have a little problem with the latest Premiere Pro CC version on multiple workstations: A red banner with the label 'This effect requires GPU acceleration' appears when using any of the VR effects except for the effect 'VR-projection'. The effects themselves don't work. CUDA-rendering is of course activated. Now here's where it gets interesting: The problem seems to occur only if the resolution of either the footage or the sequence is larger than aprox. 7250*7250 px.
We tested multiple files on different workstations. Sadly, they all have similar GPUs (GeForce GTX 980 or GTX 980 Ti with the latest drivers). All the workstations we tested it on run either Windows 7 or Windows 10. The problem occurs even when theres only one media file with a single effect in the timeline (so it has nothing to do with other effects interfering). Is there any way we can get the effects to work with 8k stereoscopic footage?