The following test fails intermittently in my stress runs:

jdk/javadoc/doclet/testLinkOption/TestRedirectLinks.java

Here's the failing snippets from my jdk-20+20 sightings on linux-x64:

Starting subtest 2.2: checkOutput TEXT allowOverlaps:false expectFound:true expectOrdered:false
FAILED: OUT: following text not found:
warning: URL http://127.0.0.1:34245/element-list was redirected to https://127.0.0.1:46649/element-list

<snip>

Starting subtest 2.3: checkOutput TEXT allowOverlaps:false expectFound:true expectOrdered:false
FAILED: api/mC/p5/C5.html: following text not found:
extends <a href="http://127.0.0.1:34245/mA/p1/C1.html" title="class or interface in p1" class="external-link">C1</a>

<snip>

Starting subtest 2.4: checkOutput TEXT allowOverlaps:false expectFound:true expectOrdered:false
FAILED: api/mC/p6/C6.html: following text not found:
<a href="http://127.0.0.1:34245/mB/p4/C4.html" title="class or interface in p4" class="external-link">C4</a>

This particular sighting occurred with linux-x64 slowdebug bits.