Trainz 2019 Keeps Adding Nonexistent Thumbnails After Editing a Session

I have this weird glitch where after spending a lot of time editing a session, it changes the thumbnail container in the config file, adds a thumbnail that doesn't exist, then marks it as faulty saying the thumbnail it added doesn't exist. Here's what it's supposed to look like:

thumbnails
{
default
{
image "thumbnail.png"
width 512
height 384
}

0
{
image "0.png"
width 512
height 384
}

1
{
image "1.png"
width 512
height 384
}
}

And here's what it keeps changing it to:


thumbnails
{
0
{
image "thumbnail.png"
width 512
height 384
}

1
{
image "0.png"
width 512
height 384
}

1
{
image "thumbnail.jpg"
width 240
height 180
}
}

How can I make it stop doing this? It's really annoying!:n:

I've noticed the thumbnail changing too, though I don't show any errors. Weird....

The DLS thumbnail is a general view of the asset, and may include identifying text or logos. This must always be 240 x 180 pixels, and must be in jpeg (jpg) format. All assets must have the default 240x180 thumbnail specified. In addition to this, different assets in Trainz may use other images in the thumbnails container for different purposes.
"Thumbnails" container - TrainzOnline
online.ts2009.com/mediaWiki/index.php/%22Thumbnails%22_container

As posted by Stagecoach above, the "default" thumbnail must be 240 x 180 pixels, not the 512 x 384 you have in your "preferred" list. I suspect that it is this that is confusing Trainz.

Change the second "1" tag in your second list to "default" - this should (theoretically) fix the problem (provided "thumbnail.jpg" actually is 240 x 180).

I'm experiencing problems now with this as well. It only started over the last few days. When editing a route, upon saving and exiting, the thumbnail for the route is now where I was editing.
Hopefully it's just a little bug that can be fixed.