Can't find neighbor of underground belt

[darkfrei]

Hi all!

I can't find neighbours in my mod.

The mod must find connected belts and replace all of them with another tier.

The problem is here:

2017-06-14 00_41_28-D__Factorio_0.15_mods_FillingBeltsUpdater_0.0.1_FillingBeltsUpdater.lua - Notepa.png (6.31 KiB) Viewed 1464 times

Actual mod version:

FillingBeltsUpdater_0.0.1.zip

(3.73 KiB) Downloaded 52 times

[darkfrei]

The first situation: I place here one belt.

2017-06-14 00_46_15-Factorio 0.15.19.png (132.29 KiB) Viewed 1463 times

Second situation:

2017-06-14 00_47_28-Snipping Tool.png (114.19 KiB) Viewed 1463 times

Here is three errors: one belt changes color by enter underground only, another had changed his direction. And in the middle the belt isn't actually connected to other.

[DarkSlayerEX]

Did you mean to place the top express underground belt backwards...?

Underground belts also shouldn't connect if they aren't the same type.

Normal underground belts won't connect to fast or express versions, unless something odd changed..

[darkfrei]

I want to replace the yellow underground belt with another, for example with red or blue one.
But this replacing can't be done right way, and I don't know why.