Subdocument gets some new unsaved modification upon master update

Writer 7.6

Let’s have one sub-document open in Writer. Let’s store it to disk, hence no more unsaved document modifications.
Let’s go now to master where mentioned sub-document is inserted.
Let’s conduct an update of master.
As soon as update completes a red lamp goes on - the Save button (standard toolbar) in sub-document.
For me personally this is a big surprise - aren’t all sub-documents read-only if it concerns handling in master? Is Writer under hood carrying out the action what the user can do when she double-clicks sub-document entry in master navigator? If yes, what kind of modification does master update conduct in sub-document under the hood?

Unless you configured your master for sub-doc update, Writer will never do such a thing on its own. And even with enabled sub-doc update, you, the user, must explicitly change something in sub-doc text for the “modified” flag to become active.

Be more descriptive in your procedure, otherwise only crystal balls may help.

If I only knew which details are missing in my description.

I have troubles with formatting in document view provided by master. Therefore I try to find out where could be the reason (other times to fix the problem), hence my frequent clicks onto Update button in master layout navigator.

If I only knew how to configure master (cit.) “for sub-doc update”. All I know in this regard: a master existing yet including some subs asks user for acceptance to carry out update when it gets open.

Isn’t this a question related to template styles update?
I remind you you uselessly complicated your matters by going straight for advanced usages (master + template + probably other tweaks) without mastering the basis. It is likely that your Brownian motion attempts messed up things even more.
It is very difficult to diagnose the cause of failure without seeing you in front of your computer. And your lack of fluency in English (no offence intended; it is only a fact) doesn’t help.