Steps to replicate the issue (include links if applicable):

• Enter the following wikitext:

<ref details="page 1" name="book">Miller</ref>
<ref details="page 2" name="book">Not Miller</ref>

• make any change to the page
• save the page or switch to wikitext

What happens?:
The duplicate main ref content is being overwritten:

What should have happened instead?:
Both main ref contents should have stayed as they are without subrefs:

Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):
An alternative solution could be to display an error in VE and prevent editing for this incorrect wikitext in VE, similar to the way VE handles templates in the reflist. We estimate this with S.

See also T392814: [Bug] VE renders the conflicting main content as sub-ref instead of ignoring it.