Why is Ionic bypassing my XLF translation file?

Question

I have xlf files to translate my application. My app is set to English by default, I can also switch to a French version. The tree structure is as follows:

src/locale/
   messages.en.xlf
   messages.fr.xlf
   messages.xlf

My angular.json is set like this:

{
  "projects": {
    "app": {
      "i18n": {
        "sourceLocale": {
          "code": "en",
          "baseHref": "/en/"
        },
        "locales": {
          "fr": {
            "translation": "src/locale/messages.fr.xlf",
            "baseHref": "/fr/"
          }
        }
      }
   }
}

The translation is done in most cases, but there's one case where it's not and that drives me crazy, I must be missing something.

For example, here is a part of my html:

   <ion-row *ngFor="let person of listOfPersons" (click)="doSomething(person)">
         <div>
            <ion-row>
               <ion-col size="10.5">
                  <ion-row>
                     <ion-col class="title" size="4" i18n="fullname"> Firstname Lastname </ion-col>
                     <ion-col class="content" size="8" data-e2e="myfullname"> {{ person.firstName}} {{item.lastName}}
                  </ion-col>
               </ion-row>
            </ion-col>
         </ion-row>
      </div>
   </ion-row>

And here is my messages.fr.xlf

      <trans-unit id="XXX" datatype="html">
        <source> Firstname Lastname </source>
        <target>Nom/Prénom</target>
        <context-group purpose="location">
          <context context-type="sourcefile">src/.../my.page.html</context>
          <context context-type="linenumber">22</context>
        </context-group>
        <note priority="1" from="description">fullname</note>
      </trans-unit>

And my messages.en.xlf and messages.xlf are exactly the same without the target tag.

In the French version, I have "Nom/Prénom" which is correct.

Now, I want to change "Firstname Lastname" by "Lastname", so I did it everywhere there was "Firstname Lastname" (html file + the 3 xlf).

The French version is now showing Lastname instead of "Nom/Prénom", and I don't know what I'm doing wrong.

I tried all combinaisons, but I didn't get it working. Everything seems correct to me, I even added line number (which corresponds) so I don't get it.

Thanks for your help

EDIT: I tried something else. I replaced "Firstname Lastname" by "Lastname", except in HTML where I kept "Firstname Lastname" -> French version is showing "Nom/Prénom" which is correct, how is it possible? Same thing, if I put "Lastname" in my HTML, I get "Lastname" in French version instead of "Nom/Prénom".

It seems that all my messages.xlf are bypassed, and of course there are no others "Firstname Lastname" in my project.