When I look at the page for downloading firmware it displays
Cybook Odyssey Firmware Update - Version 5.2 (build 1780)
Is that the latest release, I red somewhere about version 5.2 build 1894 also.
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If you sync via WiFi you should get version 5.2 build 1894. You can check if you have that version via the Settings → About ... menu.
The manual download page might be out of date with the actual version of CybUpdate.bin you download from there, or the download itself might be the 1780.
I have never tried to install that 1780 version as my Bookeen came with build 1894 and has not wanted to upgrade via WiFi (so I assume I have the latest version).