The config value is fixed. Three file system problems remain in /srv/stock-api: current points at a release that was never fully deployed, logs/ is owned by root so stock cannot write it, and data/stock.csv is writable by every user.

Inspect each one before you change it:

ls -l
ls releases/*
ls -ld logs
ls -l data/stock.csv

Fix them with ln -sfn, sudo chown, and sudo chmod. Use the smallest change that works.

Check with ls -l again: current should point at a complete release, logs/ should belong to stock, and the data file's mode should end in - for others' write.