The description of the deployment variable bamboo.build.working.directory given on https://confluence.atlassian.com/bamboo/bamboo-variables-289277087.html
is 'the path to the working directory for Bamboo. This is used by both the build plan and the deployment project'
But this variable is job-specific, as its listing under Build-specific variables makes clear:
'The working directory on which the build is being executed, for example <HOME>/xml-data/build-dir/AV-AVT-JOB1.'
If it has a different value for each job in the build plan, then which value is available to the deployment project?