I'll have a go at replicating it so just to be clear its something like:
Note 1:
[attachment_jan](:/abc...)
Note 2:
[attachment_feb](:/def...)
You then rename Note1 to Summary and copy Note2's attachment data into Summary so it now looks like:
Summary:
[attachment_jan](:/abc...)
[attachment_feb](:/def...)
Then you delete Note2 and the resources no longer show up and are being deleted?
Also, just for information, what is your note history config set as?
Also what Joplin version and OS?