Capture One, Photoshop and Javascript

I have this very strange workflow problem. Once files are outputted from C1 they go to a temp folder (any one of 10 folders) where a custom Photoshop controller picks them up and produces 5 different resolution jpgs. About 1 in 10 to 15 files requires a sky to be stripped in in Photoshop. Once the sky is in place an action flattens the image and runs a simple Javascript which changes the Save as... string from /final to /temp so all 5 files will update.

This all ran smoothly until we updated to 4.7. After we updated at odd occasions when the action was run the file flattened and then an error message saying "Cannot save the file as it is open or in use" started appearing. This does not happen when C1 is shut down. At first we thought it was caused by the temp folder being in the Favorites list or if there was a C1 Cache in the temp. But it then started happening regardless of these conditions.

It doesn't happen all the time, maybe once every 3 or 4, but once it starts it doesn't stop until C1 is closed and seems to be becoming more frequent. It is definitely caused by C1 as if C1 is closed it never happens.

Any help would be greatly appreciated.

Regards,

Terry