CRASH on H.265 job

[bubffm]

I keep getting the following error message when tryin to encode a proRes file into H.265 using the Hybrid frontend 

I can't make sense out of it. Anyone any idea?

Importing HEVC: |====================| (100/100)                                                        HEVC Import results: 3354 samples (3510 NALUs) - Slices: 31 I 760 P 2563 B - 78 SEI - 26 IDR Stream uses forward prediction - stream CTS offset: 3 frames  Error: Feature Not Supported

Many thanks
Burkhard