Using maskelements based on nodeID (and maybe other fields) to match event definition doesn't work

Let's say that you want to have custom event content for the same event definition based on the associated node, for example, provide a custom operator instruction field.

One way to do this is by creating multiple copies of the event in question, and add to each of this copies a custom mask that would have something like this:

<maskelement>
   <mename>nodeid</mename>
   <mevalue>~10[123]</mevalue>
   <mevalue>110</mevalue> 
</maskelement>

Then, update the fields that should have a custom content like the operator instruction.

The only requirement is that these new events are placed on a file referenced before the file on which the original event is defined.

This used to work as expected until Horizon 19 came out.

It turns out that HZN-978 has broken this feature. I was able to validate this by reverting the changes of this particular enhancement on a branch of 19.1.0, and the matching feature work again.

As the changes introduced on HZN-978 are important, the idea here is to make sure to avoid breaking this feature while keeping the enhancements added to H19.