This looks like a sandboxing issue, can you please remove the source folder in the “Media Locations” tab in X2Pro5 (three clicks) and add the folder that contains the media again (drag n drop) back into “Media Locations” and advise.
We have seen this error message on Sonoma 14.# before and is due to the Sandboxing in the later Mac OS versions.
A general Workaround is to refresh the ‘Destination AAF Folder’ in X2Pro5. E.G. Drag a different folder into the ‘Destination AAF Folder’ and the Drag the actual ‘OMF FCP J2 TEST’ folder back into it.