Issue regarding custom models

[Acies]

Odd that the OpenCollada exporter doesn't work, I do not remember wheter the installation was causing a fuzz or not at the time I was installing it. See if you can find a way to make it working (I may have had to search for a solution but I'm not quite sure - it was about a year ago).

As for temporarily fixing your issue have you tried making a compound of the walls? Aligning two of them and then pressing B should center the pivot point and allow for easier future placement.

I have found that model exporting to Amnesia is best suited using the OpenCollada plugin, while the FBX export may cause issues.