Would you mind to specify your actual software configuration (3ds Max, RC & renderer versions used)? Thanks in advance. Please feel free to send us
your scene and we'll have a look at it here. Ideally, could you try to reproduce the problem with a minimal scene and send us such a scene? Thanks in advance for any further comments on this issue you can share about it with us / our user community (in case some user(s) will run into similar troubles).