dos attributes are not available for unreadable files.
Have patch, need bug number.
I just saw that Ralph fixed the same problem (for gpfs only though) back in 2017 already, see bug 12944
This bug was referenced in samba master:
Created attachment 16570 [details]
backport for 4.14 and 4.13
the backport is fo 4.14 only, not 4.13 as I wrote above.
looking at the issue in 4.13 confused me quite a but: 4.13 had this *almost* correct. After 4.13 the new code from d466ba6d61365f72618dd3093706b8706b8f7c93 that replaced the old get_ea_dos_attribute code that was removed in 3db25c1c9b3f0d5ec91905b068a0da3daa581e02 had a errno == EACCES conditioned become_root.
To make the long story short, in 4.13 just the errno==EPERM condition was missing in get_ea_dos_attribute. I leave 4.13 alone though. master has it right now and 4.14 should get the backport.