Unfortunately I haven't been able to establish a real solution for this error. However the problem lies in the downloaded file being corrupted.
I recommend going to the folder in which you have the BannerlordOnline launcher installed (not the module folder). You may need to delete the
Release_890352137 file located there so that it will re-download the file. The number in the file name may vary depending on language settings and last downloaded version.
View attachment 1944