Looking at the error it seams to be visable in the system log. I can see that the system is adding port 443 to the end of the domain. log shown below

Jul 11 2017 10:43:21.309 19000 14180 4 StartUserAction,User,Action 1 1411
Jul 11 2017 10:43:21.477 19000 14180 5 Using Local server internally: http://localhost
Jul 11 2017 10:43:21.478 19000 14180 5 START - doEndpointPost URL: http://localhost:443/sdata/crmj/async/spreadsheetTask?trackingId=E9E11160-0C33-4C05-982E-3A518742CB35&type=XLSX&root=c%3A%5Cprogram+files+(x86)%5Csage%5Ccrm%5Cvwgfbc%5Cwwwroot%5CTemp%5CTemporary+Excel+Files%5C&inputfile=c%3A%5Cprogram+files+(x86)%5Csage%5Ccrm%5Cvwgfbc%5Cwwwroot%5CTemp%5CTemporary+Report+Files%5Cadmin-20170711104321346.XML&SID=22478522235709
Jul 11 2017 10:43:21.484 19000 14180 1 CRMOpenThreadTokenWinVista
Jul 11 2017 10:43:26.600 19000 16624 4 StartUserAction,User,Action 254 362

on the test system this does not happen.

Jul 11 2017 10:37:09.368 5580 8492 4 StartUserAction,User,Action 1 1411
Jul 11 2017 10:37:09.419 5580 8492 5 Using Local server internally: http://localhost
Jul 11 2017 10:37:09.420 5580 8492 5 START - doEndpointPost URL: http://localhost/sdata/crmj/async/spreadsheetTask?trackingId=9D73FFC6-B8F9-4191-B3DF-9BEE39865E4E&type=XLSX&root=c%3A%5Cprogram+files+(x86)%5Csage%5Ccrm%5Cvwgfbc%5Cwwwroot%5CTemp%5CTemporary+Excel+Files%5C&inputfile=c%3A%5Cprogram+files+(x86)%5Csage%5Ccrm%5Cvwgfbc%5Cwwwroot%5CTemp%5CTemporary+Report+Files%5Cadmin-20170711103709382.XML&SID=72337352034273
Jul 11 2017 10:37:09.423 5580 8492 1 CRMOpenThreadTokenWinVista

Does anyone know where the system generates this from?

Thanks