The pi 3's built in wi-fi wasn't very good, so it would cut out randomly, primarily due to interference (like driving too close to the furnace), causing the entire site to be inaccessible briefly, and users would see the reverse proxy site-down message.
This issue was addressed in later roombas with better USB wifi adapters and a separate server for the client-facing website, allowing for smoother handling of network interruptions.
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Photos of the now disassembled original roomba rover:
