[vitro]

I am using two signal objects per signal to achieve better looking light. These objects using two different LightTextures: background and actual signal lense. But I getting two different results depending on train start location using exactly the same signal shapes. Here's some images:
https://i.imgur.com/Rup0H2G.png
https://i.imgur.com/r5zUIno.png
In first case all is going fine and signal has its nice appearance.
On second picture there is a place approximately 3km away from first screenshot point. Now rendering order of textures have changed and backlight texture hiding behind front lense image. If i start on first location and move camera to second screen place then appearance of signal would be correct.
Can anyone explain signal textures loading mechanics or help to overcome this glitch?

UPD: I've found a solution. To avoid this, first signal object in world file of this and all 8 surrounding tiles must be that, which uses background texture.