I have found those two entries and they are less than two minutes apart.

I noticed that the following entries where sitting between them:
 

05/20/24-11:05:47:140 (7248) 1 [Utility.Event] Backup.General.ExternalFreeze: Warning, d:\intersystems\healthconnect\mgr\irislocaldata\ is not being journalled
05/20/24-11:05:47:140 (7248) 1 [Utility.Event] Backup.General.ExternalFreeze: Warning, d:\intersystems\healthconnect\mgr\hslib\ is not being journalled

I don't know why they weren't journalled, but when I set to be journalled, the error I initially reported has since disappeared.

Thanks for your comment, it help me solve my problem.

UPDATE

I was making a mistake - the file I was using was is the empty schema. I needed something that contains valid content, such as the example given here.

When used that file, the Rest Command Line Interface Worked correctly.

I've found out what I need to do with the following link, a section titled "Predicate Conditions and Streams" from the page "Storing and Using Stream Data (BLOBs and CLOBs)"

https://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY...

I solved it.

I changed to OnPage() method to use a  %Stream.FileCharacter as follows:

ClassMethod OnPage() As %Status
{
	
	set fs = ##class(%Stream.FileCharacter).%New()
	set fs.Filename = %request.Get("filepath")
	
	do fs.OutputToDevice()
	quit $$$OK	
	
}