Solved - Question : Kodi do auto clear a property ?

Hi, i came here because i detected a 'strange' behaviour.

I set up a view type, with cutom panel containers (at season level).

One of them has  a static item which set a property onclick  (- which starts trailer in windowed mode)
My first attempt was to give the prop a simple name.

<item id="9">

                        <label>Local Trailer</label>

                        <label2 />

                        <visible>!String.IsEmpty(Window(home).Property(trailer_avail))</visible>

                        <onclick>SetProperty(TrailerPlaying,true,home)</onclick>

                        <onclick>PlayMedia($INFO[listitem.path]$INFO[ListItem.FolderName,,-trailer.mp4],1)</onclick>

                        <icon>$INFO[ListItem.Art(tvshow.landscape)]</icon>

                        <thumb>$INFO[ListItem.Art(tvshow.landscape)]</thumb>

                    </item>

I decided to set property because i want to hide some controls with a fade animation.
And i thought i have to clear it, but KODI does it for me ;-) ..

If i name the property

<onclick>SetProperty(TrailerPlaying,true,home)</onclick>

KODI auto Clears that prop, after i quit/stop playback. (press 'x' key

And/But if use
<onclick>SetProperty(TrailerIsPlaying,true,home)</onclick>

I need to Clear the Property via XML , which is my Expected behaviour.

Can someone tell me, why that happens ?
Or lead me to a source with 'KODI native (gui) propertys ' , so i have control over which naming conventions for custom propertys i should avoid ?!


Link to Video for retrace