Hello and good morning,
Lets see if I can help you out. From your post, I see two issues that are easily solved.

lets cover the most colourful one first.
1) Flashing textures:Flashing texture means that there is a missing texture that the model is looking for. This is the default "Missing" texture to let developers know something is wrong visually. Normally you can see the error in your error panel as well. This error will tell you that the texture is missing, and what one and the location it is looking for it.
Though the texture is annoying other engines do the same thing, though they tend to use a white or grey texture. HE uses the annoying flashing texture to let you know to fix the issue and remove that extra overhead of the server continually looking for the missing texture.
Make sure when you do replace them, you have them in the same directory structure locally as what is on your server.
Note: You can put or move your HE root directory anywhere you like, but make sure that everything inside ../HE/.. matches. But make sure that your files (Models and textures) in your models are in the correct place inside the HE directory and matches your export and import on the repository.
2) Material Redefinition:For the same textures being applied that is due to a model looking for the same material as another asset. It will generally apply the texture based on the first model and texture loaded.
This error can also be seen in the error panel as "
Material Redefinition".
Example: These textures are different for two different models from two different files, but HE looks for material names for that model file.
model_01 has the material named "default_01"
model_55 has the material named "default_01"
When model_01 loads first, it will apply the correct texture, but once model_55 loads it lookks for that material, then applies it, with the incorrect texture.
The solution to this is to make sure that your materials are named different for every file. I tend to use the model/file name as a base for my materials. I also tend to group similar or sets in the same max (or maya) file so I can utilize both texture and material banks.
Example: Using the max or model base name as your base for your material names removes the Material Redefinition:
Max file: MyModel_00
Model name: MyModel_01
Texture Name: tx_MyModel_01
Material Names: MyModel_00-a, MyModel_00-b, MyModel_00-c
This is a brief overview. I hope that this helps. Please feel free to ask any other questions you may have, about this or other issues. We are here to help.
