After upgrade to this version duplicati-2.2.1.0_beta_2026-03-05-linux-x64-cli.deb GUI does not store change of dblock-size. It removes that option from json. And defaults backup to 50MB.
When I import manually modified json backup config with custom value of 512MB with “Import Now” (skipping rest of GUI wizard) and later I export to verify - option is there, and running the job is working with desired value.