"Lazy resolver" feature introduced in v3.11.0 slows down expanding operations in OAS3 spec

Q&A (please complete the following information)

• OS: Windows 10
• Browser: Chrome, Firefox
• Version: Chrome 71, Firefox 65
• Method of installation: swagger-ui dist in IIS
• Swagger-UI version: 3.10.0 vs 3.11.0 - 3.20.6
• Swagger/OpenAPI version: OpenAPI 3.0

Content & configuration

Example Swagger/OpenAPI definition:
https://pastebin.com/raw/Zh5ZGN17
Note: This spec is obfuscated

Swagger-UI configuration options:
Swagger editor default settings

Describe the bug you're encountering

In version 3.11.0, the "Lazy resolver" feature was introduced, which is supposed to significantly improving performance. However, using our OpenAPI 3.0 spec (see link above), the performance dramatically drops instead of improves.

For example, when clicking operations GET /HHUTVNQGQCUN or GET /KAYQPVEJWLYY, you have to wait a really long time (varying between 2 and 20 seconds). When rolling back to version 3.10.0, the performance is back to less than 1 second. I have also tried the latest version 3.20.6, and that's also very slow.

When using the Swagger 2.0 spec of (a slightly older version of) the same API, there are no performance issues.

To reproduce...

Steps to reproduce the behavior:

1. Click GET /HHUTVNQGQCUN or GET /KAYQPVEJWLYY to expand the operation
2. Wait

Expected behavior

Operation expansion in less than 1 sec

Start by loading the obfuscated OpenAPI 3.0 definition from the linked pastebin in Swagger UI 3.10.0 and a 3.11.0-or-newer version, then reproduce expansion of GET /HHUTVNQGQCUN and GET /KAYQPVEJWLYY. Compare the lazy resolver behavior and measure whether those operations expand in under one second, matching the Swagger 2.0 comparison.