This issue looks similar to Bug ID -- 705447.
Suspecting the commit from the CL --
https://chromium.googlesource.com/chromium/src/+log/d59c57610403a5ae1b1f3f7a0af323ba53ff0a01..e84bdf15a68877a3a2962abaeb0827081a7ca17d?pretty=fuller

Commit#
https://chromium.googlesource.com/chromium/src/+/baf4f1f0cca9c704ff01de23e9360a1deef00cb4

@jochen -- Could you please look into the issue, kindly re-assign if this is not related to your changes.
Thank You.

ClusterFuzz has detected this issue as fixed in range 472378:472409.

Detailed report: https://clusterfuzz.com/testcase?key=5274009970409472

Fuzzer: bj_broddelwerk
Job Type: linux_ubsan_vptr_chrome
Platform Id: linux

Crash Type: CHECK failure
Crash Address: 
Crash State:
  !contentFrame() in HTMLFrameElementBase.cpp
  blink::HTMLFrameElementBase::didNotifySubtreeInsertionsToDocument
  blink::ContainerNode::insertNodeVector<>
  
Sanitizer: undefined (UBSAN)

Regressed: https://clusterfuzz.com/revisions?job=linux_ubsan_vptr_chrome&range=436291:436296
Fixed: https://clusterfuzz.com/revisions?job=linux_ubsan_vptr_chrome&range=472378:472409

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5274009970409472


See https://dev.chromium.org/Home/chromium-security/bugs/reproducing-clusterfuzz-bugs for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.