SourceOne for File Systems: Re-index of a Virtual folder on a File Index in place archive folder is broken after upgrade to 7.2.6

User has recently upgraded SourceOne Email Management to 7.2.6 and he is running SourceOne for File Systems.
User has a File Index in place archive folder which contain some indexes with errors and he is attempting to Reindex an Index set.
The reindex operation fails with the following errors in the ExAsIdxObj.exe.log or the ExAsElasticIdxObj.log:

Unable to add messages in volume 20181233444555 to index, marking index as having missing items

Marking local idx state as missmsg c:\Work\EMC SourceOne IndexWork\virtual_201811_001\Index
[E:\Work\EMC SourceOne IndexWork\virtual_201811_001\Index] Initial m_pOpenDatabase failed with 2016, 'ERROR:  No ISYS index in directory: E:\Work\EMC SourceOne IndexWork\virtual_201811_001\Index\'.  Attempting fixup.

Unable to open isys.ixb file for fixup E:\Work\EMC SourceOne IndexWork\virtual_201811_001\Index

This issue is resolved in patches or Service Pack versions of EMC SourceOne Email Management post 7.2.7.7017 (HFB 1).

Hotfix Bundles and Service Pack kits are available for download via https://www.dell.com/support.
* Please note, Hotfixes are only available for the most current patch or Service Pack versions of the product that were available when this problem was resolved.
** Please note that it is always recommended to upgrade to the latest version of the SourceOne release, service pack and Hot Fix Bundle to ensure all currently resolved issues will be fixed including the issue as stated above