Securities Register Add-On; Reply to Security Item log not saved

When replying to a Security Statement Item Log via the Security Statement form, Logs page, and clicking the 'Reply to Log/Continue thread' button at the bottom of the Logs grid, the following message was displayed:

'Failed to save Security Statement Item Log.

Invalid ParentLogPk. ParentLogPk must exist and all Logs within the same Thread must link to the same Security Item.'