User Name Appears as Last updated for Tasks which the user never updated it

Document ID : KB000111065
Last Modified Date : 10/10/2018
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One of the users has made updates only to the risks, issues and phase attributes and made no updates to the Tasks. However in the system it shows his name as updated for Tasks. Not sure why does this happen?
DE43325 - Why does a simple save at project level update Task last updated fields?
Fixed in 15.5.1
Patched in and