Numbering is missing on body.getOoxml() in Word 2016 MSO - ms-word

Question

Using body.getOoxml() in an add-in for Word 2016 does not include the numbering package part. This leads to errors when executing insertooxml() since the API creates new numbering definitions which are wrong or default to the standard (as 1,2,3 etc.). Hence numberings that have other logic, like lower letters or roman letters, will be set back to the standard on executing insertooxml().
This applies to Word 2016 MSO which still uses IE 11 in add-ins. (nothing we can do about that).
In Word for M365 it works correctly.
The Word version in use is 16.0.5369.1000 MSO 16.0.5366.1000 32-Bit (Running on Windows 10)
We currently use Office-js version 1.1.82 (the newest 1.1.83-custom.0 has a bug that throws an exception on insertooxml in Word 2016)
We need this for our solution which removes sensitive data from word documents. Since Word Js Api 1.1 does not include hyperlinks, we need to operate on ooxml to fix hyperlinks as well.
Steps to recreate:
Create a new word document
Add one or two titles
Change title numbering to "a,b,c"
Execute the following code in an add-in:
var body = context.document.body;
var body_ooxml = body.getOoxml();
await context.sync();
var body_ooxml_value = body_ooxml.value;
body.insertOoxml(body_ooxml_value, Word.InsertLocation.replace);
await context.sync();
What I expected:
The content of the document should remain the same. Without any changes to the numbering
current findings
I made several tests and found out that in Word 2016 MSO, getOOXML does not return the numbering - even though the file numbering.xml exists and is correct. After executing insertOoxml it seems as if the api is trying to re-create the numbering from scratch which leads to an overwrite in numbering.xml that includes standard numbering (1,2,3).
I don't see a workaround (but would be happy for any advice).This seems to be a product bug and needs to fixed.

Answer 1

Just FYI, in case you didn't know: Microsoft no longer requires support for IE in add-ins that are distributed through AppSource. That said, it does seem to be a bug, so you could create a bug issue on the office-js repo. But I don't think a bug in an Office version that old will have a high priority.