Created attachment 127103 [details]
file with case showing calculation error
It seems that when the last computed workday coincides with a holiday, WORKDAYS.INTL seems to ignore it.
The file attached has this situation
Start date: 8/31/2016
Number of days : 5
Calculated value: 9/7/2016
Expected value: 9/8/2016
Upon a closer look, this is the same issue as bug 101541.
*** This bug has been marked as a duplicate of bug 101541 ***