quoted

How do you think about to resolve them by additional means besides mail exchange?

That can work.

I am curious to find out which other communication means could really help here.

E.g. meeting at conferences often solved mail communication problems.

I find my resources too limited at the moment to attend conferences on site.

How are the chances for further clarification by ordinary telephone calls?

For now, I still wonder why you were unsure about grouping the changes
into one patch?

I am varying the patch granularity for affected software areas to some degree.
But I came also places along where I got an impression for higher uncertainty.

Maybe there is something to be learned?

This is also generally possible.

Would you like to extend the scope for the change pattern around questionable
error messages from a single source file to whole subsystem trees in Linux?

Regards,
Markus