Hi Francesca,
if you run FLAIR from the centralized (customized!) installation on CERN’s RP cluster, you need to run it via the command “flair3”. Just running “flair” will not work on the cluster but it might work in your private installation (e.g. virtual machine or local machine) which is administrated by yourself.
For the centralized installation I have deployed a patch which hopefully fixes the issue. If you want to apply it on your private installation then you need to follow the instructions that I have provided here: Geoviewer tab-Segmentation fault
Without going into too many technical details: the 3D renderer tries to do several things in parallel to be faster and for this it needs to spawn multiple threads. Some CPUs (specific virtual machine configurations or older CPUs) might not be able to provide multiple threads and this rather exotic situation was previously not yet caught by the renderer when doing specific tasks to improve the image quality.
Cheers
Chris