Describe the bug
My A1 Peppercorn locomotive disappeared without a trace while it was going around the top track of my oval. This was not long after I loaded the world and all I was doing was look at my performance numbers which were not as they used to be.

How to reproduce
I loaded my world and this happened. No clue on what steps as I personally only looked around and admired the bad frames.

Expected behavior
A1 Peppercorn locomotive to not disappear.

Screenshots

The A1 tender is still rolling on its momentum.

System Information
OS: Windows
System Memory: 8GB
Allocated Memory: 4616 MB
CPU: AMD Phenom II X4 955 Black 3.2Ghz
GPU: AMD Radeon HD 6670 1GB
IR-Version: 1.7.1_1.12.2
Forge-Version: 14.23.5.2847

Modlist
https://paste.dimdev.org/oqugigogun.txt

latest.log
https://paste.dimdev.org/fakehifuwe.log

Additional context
The save file I loaded: http://cyanox.nl/a-ir_1.7.1_bug.zip .
This is a save from before I updated to 1.7.1. If loaded this should be roughly the same. This is a test world and may need the entire pack with configs to be loaded so here: http://cyanox.nl/a-ir_1.7.1_bug_pack.zip .

There are a few things I noticed in the log when loading the world (line 4351 and beyond):

1:

[14:46:03] [Server thread/WARN] [FML]: The mod immersiverailroading has registered persistent chunkloading data but doesn't seem to want to be called back with it - it will be removed from the world save

This worries me as incorrect chunkloading and unloading has been a major issue in the past for me when maintaining servers.

2:

[14:50:55] [Server thread/WARN] [universalmodcore]: Coupled entity was not loaded after 20 ticks, decoupling
[14:50:55] [Server thread/INFO] [universalmodcore]: f6c598c4-a187-4640-92ea-fc703a239a00 decouple Front

I think this is where the locomotive was discovered "gone" but no errors or indications as to why it was gone just before it.

coupled entities is simply saying that after so many ticks, the object would not regester that it was connected to a train. however if the mod refused to load an item, i can see why you have the item disappearing. i will pass this on to the others and see if they can come up with a fix

@NoxyNixie upgrade IR please, new version forces chunkloading on non-moving stock which may help your issue.