Unable to Merge Applications in 'Vacancy Maintenance' screen

The process runs out of memory when trying to merge a large number of applications simultaneously. The number of applications it is possible to merge at the same time will depend on how many documents per employee (CV, qualifications, images) are included. It is possible to generate a larger number of applicants where there are not as many additional documents, and fewer when there are more documents or large images.
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Break up the merging of applications into smaller chunks of ~20 applicants per merge, or as many as can be combined at the one time.