Deleting items does not update instrumentation

Reproduce:

* On a blank page, create 3 sections
* Delete the middle section
* Delete the last section, previously section 3, now section 2
* It will try to delete section 3, which it doesn't find anymore, since the ue service now refers to this as section 2 when it re-pulls the instrumented document
* Reload the page, and deleting section 2 works again

Reproduce the sequence on a blank page: create three sections, delete the middle section, then delete the last remaining section. Trace how deletion targets are updated when the UE service re-pulls the instrumented document. Done means consecutive deletions use the current section numbering and continue to work without a reload.

Written by the indexing model from the issue text.