I started a completely new PLN to see if erors as in previous posts occur again.
After modelling a bit I started the plugin and this error occured:
I closed the plugin, re-opened it and no error appeared this time.
I saved the PLN, closed Archicad re-opened the PLN and the materials are without textures????
I opende the AC material library and closed it again.. the materials are OK with textures again.
I closed the PLn without having opened the plugin and it is without textures again!.
I made another scene from blank (using the standard template) with textures and did not open the plugin at all, saved the PLn and opened it again. This test is to make sure it is not an Archicad thing

The textures are OK this time.
Now again I opened the plugin (without opening OR viewport) and closed it without doing anything else. Textures are OK.
This time I open the OR viewport and close and re-open the file: everything is still OK!
next test are with closing PLN and open everytime:
next test: add an AC object: OK!
next test: import material to AC wall OK!
next test: add proxy to the AC object: OK!
next test: add scatter to the proxy: textures are OK, but scatter is not done !
next test: add scatter again to the proxy: textures are OK, but scatter is not done !
The last file I cannot replicate the texture error again, but only got the csv-not-loading.
@Paul, Can you make up anything from this?