Cross-references fail to resolve on big `xrefmap.xml` file

[frarees]

Operating System: macOS Big Sur 11.6 (20G165) DocFX Version Used: 2.59.2.0 (brewed) Template used: default

Steps to Reproduce:

Attached there's a Unity project with two configs: docfx_tiny.json and docfx_complete.json

unity-test.zip

1. Download unity-test.zip and unzip.
2. Run docfx build docfx_project/docfx_tiny.json --force. See how it resolves a valid StartCoroutine_Auto reference.
3. Run docfx build docfx_project/docfx_complete.json --force. It doesn't resolve a valid StartCoroutine_Auto reference.

Both xrefmap files define this entry:

- uid: UnityEngine.MonoBehaviour.StartCoroutine_Auto(System.Collections.IEnumerator)
  name: StartCoroutine_Auto
  href: https://docs.unity3d.com/Documentation/ScriptReference/MonoBehaviour.StartCoroutine_Auto.html
  commentId: M:UnityEngine.MonoBehaviour.StartCoroutine_Auto(System.Collections.IEnumerator)
  fullName: UnityEngine.MonoBehaviour.StartCoroutine_Auto
  nameWithType: MonoBehaviour.StartCoroutine_Auto(IEnumerator)

Expected Behavior:

DocFX resolves big xrefmap.xml files (sample file attached is ~14mb).

Actual Behavior:

xrefmap with one entry:

big xrefmap (containing the entry present in the previous xrefmap, but not resolved):