Problem loading branches in the webinterface

Hi there,
I am using feature-branches called “feature/XXXX” which are pushed to my GitLab-CE 10.1.4 (+Apache).
Now when I try to access the repository inside my browser it seems to work fine until I switch to the feature-branch. I then get an “Something went wrong on our end.”-banner eventhough I can see all commits etc just fine.

In my log I can see the following:

Started GET "<group/repository>/tree/feature/registrations" for <IP> at <DATE>
Processing by Projects::TreeController#show as HTML
      Parameters: {"namespace_id"=>"<NAMESPACE>", "project_id"=>"<PROJECTID>", "id"=>"feature/registrations"}
    Read fragment views<group/repository>/c7b09881d1401b078060bdcf1cbb133b6d64bde5/application_settings/3-20170908161508393276000/0//false/en/579253818c44ab22078f8d68f20179d9 (0.3ms)
    Completed 200 OK in 166ms (Views: 127.8ms | ActiveRecord: 11.0ms)

    Started GET "/uploads/-/system/user/avatar/3/IMG_20150322_185923.jpg" for <IP> at <DATE>
    Processing by UploadsController#show as HTML
      Parameters: {"model"=>"user", "mounted_as"=>"avatar", "id"=>"3", "filename"=>"IMG_20150322_185923.jpg"}
    Sent file /opt/gitlab/embedded/service/gitlab-rails/public/uploads/-/system/user/avatar/3/IMG_20150322_185923.jpg (0.1ms)
    Completed 200 OK in 8ms (ActiveRecord: 0.5ms)

    Started GET "<group/repository>/blob/feature/registrations/README.md?format=json&viewer=rich" for <IP> at <DATE>
    Processing by Projects::BlobController#show as JSON
      Parameters: {"viewer"=>"rich", "namespace_id"=>"<NAMESPACE>", "project_id"=>"<PROJECTID>", "id"=>"feature/registrations/README.md"}
    Started GET "<group/repository>/refs/feature%252Fregistrations/logs_tree/?_=1511119425248" for <IP> at <DATE>
    Started GET "/uploads/-/system/appearance/header_logo/1/apple-touch-icon.png" for <IP> at <DATE>
    Processing by UploadsController#show as HTML
    Processing by Projects::RefsController#logs_tree as JS
      Parameters: {"model"=>"appearance", "mounted_as"=>"header_logo", "id"=>"1", "filename"=>"apple-touch-icon.png"}
      Parameters: {"_"=>"1511119425248", "namespace_id"=>"<NAMESPACE>", "project_id"=>"<PROJECTID>", "id"=>"feature%2Fregistrations"}
    Started GET "/uploads/-/system/project/avatar/57/apple-touch-icon-144-precomposed.png" for <IP> at <DATE>
    Processing by UploadsController#show as HTML
      Parameters: {"model"=>"project", "mounted_as"=>"avatar", "id"=>"57", "filename"=>"apple-touch-icon-144-precomposed.png"}
    Sent file /opt/gitlab/embedded/service/gitlab-rails/public/uploads/-/system/appearance/header_logo/1/apple-touch-icon.png (0.1ms)
    Completed 200 OK in 9ms (ActiveRecord: 0.6ms)
    Completed 200 OK in 104ms (Views: 0.9ms | ActiveRecord: 2.0ms)
    Started GET "/uploads/-/system/group/avatar/8/logo-2.jpg" for <IP> at <DATE>
    Processing by UploadsController#show as HTML
      Parameters: {"model"=>"group", "mounted_as"=>"avatar", "id"=>"8", "filename"=>"logo-2.jpg"}
    Sent file /opt/gitlab/embedded/service/gitlab-rails/public/uploads/-/system/project/avatar/57/apple-touch-icon-144-precomposed.png (0.1ms)
    Completed 200 OK in 13ms (ActiveRecord: 0.6ms)
    Sent file /opt/gitlab/embedded/service/gitlab-rails/public/uploads/-/system/group/avatar/8/logo-2.jpg (0.1ms)
    Completed 200 OK in 10ms (ActiveRecord: 0.9ms)
    Filter chain halted as :assign_ref_vars rendered or redirected
    Completed 404 Not Found in 29ms (Views: 13.6ms | ActiveRecord: 1.0ms)

    Started GET "/-/metrics" for 127.0.0.1 at <DATE> +0100
    Processing by MetricsController#index as HTML
    Filter chain halted as :validate_prometheus_metrics rendered or redirected
    Completed 404 Not Found in 1ms (Views: 0.5ms | ActiveRecord: 0.0ms)

I am just guessing but maybe it is because of this 404? Hope anyone here has an idea what it might be.
For the other non-feature-branches it works well.

Best,
Marc