error 500 when trying to use an external minio storage as object store. This happens as soon as I try to upload an image for a profile, project or a group

Hello toegether, I am trying to use my central minio instance instead of the one that comes with gitlab helm chart. I assume my configuration is fine as I am also able to execute a restore from backup task. I have read a couple of things here regarding potential workarounds. However, they seemed to be from older gitlab versions. I am currently at healm chart version 2.4.6, i.e. gitlab 12.4.2

Can anybody provide a workaround?

my objectstore secret:

provider: AWS
aws_access_key_id: key
aws_secret_access_key: secret
region: "us-east-1"
host: "https://minio.example.de"
endpoint: "https://minio.example.de"
path_style: false

my storeage config:

[default]
access_key = key
secret_key = secret
bucket_location = us-east-1
host_base = https://minio.example.de
host_bucket = https://minio.example.de

my registry storage:

s3:
    bucket: registry
    accesskey: key
    secretkey: secret
    region: "us-east-1"
    regionendpoint: "https://minio.example.de"
    v4auth: true

and minio secret is set to

accesskey: key
secretkey: secret

Thanks a lot for your help!