Hi. Can you please provide a sample diagram (in Dia format) and its
exported PNG version? [*] Also, which of all the available PNG export
filters is the one showing this behavior?
You mention "some boxes". Can you identify what kind of boxes are the
ones that get exported too small? Or, seen from another perspective,
what font, size and weight is the one being rendered too wide? Can you
narrow it down as if it is a specific kind of box or a specific kind of
font?
All this info will help find the root cause for the bug and be able to
fix it.
[*] Please remember that your sample document will be made publicly
available, so you may need to create a version that does not containt
sensitive information.
Thanks.