I believe version 3.4 was the last edition of XV model firmware, on the last model of series, Signature Pro. Given how old these models are, it can be understandable that customer service would not know the details. Earlier versions of the XV models had a different cpu processor and could not be updated beyond v3.2, so perhaps the clerk was confused by this. Only minor changes followed v3.1 adding the "corner clever" improved corner behavior.
Neato Robotics does not support updating the XV model firmware anymore, superseded by the Botvac follow-on models, but the necessary files were captured in Russia, and at Vorwerk, and can be updated offline if interested. For experts only, as anything wrong can damage systems when incorrectly updating. For more information see RobotReviews.com
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