Hi, Yann.

I'm not sure what we did, but we found this issue 'fixed itself' when we re-ran the denoising procedure under MATLAB 2023b and CONN 22.a.  Afterwards, the study file opens fine under MATLAB 2025b and CONN 25b. 

Sorry I can't be more informative, but it appears possibly that this bug is related to how MATLAB/CONN handle the addition of new ROIs to an established study file.

Warm regards,
Jeff