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.
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The manual download page might be out of date with the actual version of CybUpdate.bin you download from there, or the download itself might be the 1780.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).