Congratulations You could finally work around the issue.!

Simplified:
WIJ is the on-disk image of your modified buffers.
If buffers are changed they get updated on-disk by an asynchronous background process.
The modified date is typically the last modification at file close.
writing modification date at every file update as you expect will break every file system.

Transposing your expectation to a text editor would mean to update the file and date at every new line:
I suppose you would be disappointed by the related performance reduction.

Though, from personal experience, this seems to be the standard operating style of almost every government.😉

after I called the label a second time

pls. check ^TEST or ^TEST2 before the 2nd call
if it isn't starting with a number it throws <ILLEGAL VALUE>
I see no obvious reason in your code why it should NOT be Numeric.
so in your test loop you may do a "write ^TEST,! " to check this condition   
 

what OS are you working with ?  "C:/temp/file.xslt"

• this is wrong in Windows >>>   "C:\temp\file.xslt"
• and wrong in Linux, Unix,, ...  >>>  "/temp/file.xslt"

even deleting the lock from Terminal doesn't seems to work

Whatever you try to express doesn't make sense
Any kind of LOCK  is bound just to the job that executes it
there is just no "UNLOCK" from outside except job termination.

the locking job in your screenshot is 9908
but your terminal is job 10376  
expressed in a picture:
- you try to catch a fly in your room  that is flying somewhere outside the building

Part of it (KILL, SET, TSTART, TCOMMIT, TROLLBACK) by global by process can be traced by examination of JOURNAL

There is nothing similar for Global READ
  

You may try this approach to convert JSON into a Global for search and iteration 

ClassMethod Calendar(y As %Integer) As %String
{
 s a=$lfs("Monkey,Rooster,Dog,Pig,Rat,Ox,Tiger,Rabbit,Dragon,Snake,Horse,Goat,Metal,Water,Wood,Fire,Earth") q $li(a,y\2#5+13)_" "_$li(a,y#12+1)
}

great idea::  integers as separators!

just realized the separating blank broke the line in display.

I didn't get the meaning of  Field(ge=0) immediately
I see 6 variants to achieve this in IRIS in order of my personal preference

1. use SQL NULLIF function
2. use SQL CASE..END block if more complex
3. use a custom SQL Function = ClassMethod projected as SQLProcedure
4. create a TRIGGER if this is not just a single case 
5. use calculated properties with on Change clause
6. create a customized  OdbcToLogical method 

There are eventually more options  

First bid:

• 145 by code checker
• 35 real code - the rest is text + packing + "cosmetics"

contact ISC sales, buy an appropriate license, and  you get access to WRC and the Kit repo

Last version of Caché was 2018

I see. just Sub-sessions:
  

If this is your own CSP page you may set  %session.EndSession =1

OR
you have a dummy page that does just this and you call it manually
I did it mostly during testing