http/tests/cache/disk-cache/disk-cache-disable.html
http/tests/cache/disk-cache/disk-cache-last-modified.html
http/tests/cache/disk-cache/disk-cache-media.html
http/tests/cache/disk-cache/disk-cache-range.html
http/tests/cache/disk-cache/disk-cache-redirect.html

History:
https://results.webkit.org/?suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&test=http%2Ftests%2Fcache%2Fdisk-cache%2Fdisk-cache-disable.html&test=http%2Ftests%2Fcache%2Fdisk-cache%2Fdisk-cache-last-modified.html&test=http%2Ftests%2Fcache%2Fdisk-cache%2Fdisk-cache-media.html&test=http%2Ftests%2Fcache%2Fdisk-cache%2Fdisk-cache-range.html&test=http%2Ftests%2Fcache%2Fdisk-cache%2Fdisk-cache-redirect.html

These tests are failing together in tandem. They always fail on the same test runner together. I have tried to reproduce this locally but have not succeeded yet.
They all are failing with the same message of "response source: Network" instead of Disk cache. Some test upstream may be setting a bad state or the system is falling into this state. 

Results page:
https://build.webkit.org/results/Apple-Catalina-Release-WK2-Tests/r255440%20(2570)/results.html

example diff:
--- /Volumes/Data/slave/catalina-release-tests-wk2/build/layout-test-results/http/tests/cache/disk-cache/disk-cache-redirect-expected.txt
+++ /Volumes/Data/slave/catalina-release-tests-wk2/build/layout-test-results/http/tests/cache/disk-cache/disk-cache-redirect-actual.txt
@@ -7,7 +7,7 @@
 
 --------Testing loads from disk cache--------
 response headers: {"Status":"301","Location":"unique-cacheable"}
-response source: Disk cache
+response source: Network