I have the same problem and the same API error.
I used my description for cameras for half years and everything was ok. Now I have an error. I spent several hours experimenting with different titles, editing and cutting description, but the result is the same. Then I removed Auctiva template and item was successfuly posted. I tried different templates, but the result is the same.
I cannot explain this. I like Auctiva templates and would like to use them further.