SpecFlowPlus Task behind proxy

I'm using the Azure DevOps SpecFlowPlus task in my pipeline to upload the Specflow test results to the SpecFlow+ LivingDoc extension. Everything worked fine while using Microsoft hosted agents in the cloud. But due to a policy I now have to use self-hosted build agents which are behind a proxy with self-signed certificates, which creates problems.

Without further configuration the task has this output:

Starting: Update Specflow LivingDoc
==============================================================================
Task : SpecFlow+LivingDoc
Description : Generate living documentation from your feature files or test assembly.
Version : 0.6.964
Author : techtalk
Help : https://docs.specflow.org/projects/specflow-livingdoc/en/latest/Generating/Adding-a-Build-Step.html
==============================================================================
##[error]Error: unable to get local issuer certificate
at TLSSocket.onConnectSecure (_tls_wrap.js:1088:34)
at TLSSocket.emit (events.js:198:13)
at TLSSocket._finishInit (_tls_wrap.js:666:8)
##[error]The operation was canceled.
Finishing: Update Specflow LivingDoc

Since I saw no option to disable SSL checks for the task itself, I tried to set the environment variable NODE_TLS_REJECT_UNAUTHORIZED which helps with Node-related tasks, and it also seems to do the trick here.

- task: SpecFlowPlus@0
  env:
    NODE_TLS_REJECT_UNAUTHORIZED: 0
  displayName: 'Update Specflow LivingDoc'
  inputs:
    generatorSource: 'TestAssembly'
    testAssemblyFilePath: '$(Build.BinariesDirectory)/My.Test.dll'
    projectName: 'MyProject'
    testExecutionJson: '$(Build.BinariesDirectory)/TestExecution.json'
    projectLanguage: 'en'
  timeoutInMinutes: 5

This indeed uploads the test results so that they are visible in the SpecFlow+ LivingDoc extension. But despite that, the problem now is that the SpecFlowPlus task never finishes and times out after 5 minutes which leads to a red/failed build (or orange/warning build with continueOnError: true). This never happened on Microsoft hosted agents.

Starting: Update Specflow LivingDoc
==============================================================================
Task : SpecFlow+LivingDoc
Description : Generate living documentation from your feature files or test assembly.
Version : 0.6.964
Author : techtalk
Help : https://docs.specflow.org/projects/specflow-livingdoc/en/latest/Generating/Adding-a-Build-Step.html
==============================================================================
Uploading: 386 bytes
Uploading: 147943 bytes
Upload was successful.
##[error]The operation was canceled.
Finishing: Update Specflow LivingDoc

My goal is to have a green/successful build if the upload finishes.

Any ideas what this is and what I can do?