Arranger cropping audio when flatten


When I flatten my arrangement the sections are created in full length but the audio is cropped to what looks like around 80% length. If the section is say 31 bars the audio stops abruptly at 24.2.00. This cropping happens to each section.

This project was created in 7.5. It did this in 7.5. It also does this in 10.

It’s a long project. Has it corrupted somehow? Or have I inadvertently set something within the arrangement flattening wrongly. I can’t see anything obvious though.

Suggestions to fix this would be much appreciated.
Many thanks.