There was a Drone update with the latest tag from March 18, 2022, it`s necessary to add the Flag to the Drone Env:
DRONE_CONVERT_MULTI=( true or false)

Without this Flag, you may see the following error in the Drone Server logs:

level=fatal msg="main: invalid configuration" error="envconfig.Process: assigning CONVERT_DRONE_CONVERT_MULTI to Multi: converting '1m' to type bool. details: strconv.ParseBool: parsing \"1m\": invalid syntax"

As described in this Brat Post on GitHub about built-in jsonnet functionality