This version is EOL since few years (at least nearly 2 years, the 20.08.0 version might even be older):
and feed compatibility is not guaranteed since longer / it is not guaranteed that the seen problem is not originating from known issue in the software stack.
Please use the more Greenbone Community Edition 22.4 (stable, initial release 2022-07-25) and try again.
Note: Not sure how easy it is to update 20.08 to 22.04 so it might be required to rebuild the scanner host from scratch by following: