Menu Manager broke in 3.3.0

[datiswous]

Just installed GS3.3.1a on local server. created 3 extra pages. Added them to the menu. Move them around in menu manager, save menu, move them around again, save menu. Works fine.
Installed i18n plugin. Enabled i18n (not base). I go to Edit Navigation Structure page. Change menu order, save. Looks like saved. I check front end, menu order is not changed. Change menu order again, same situation.

This was done with debug mode on. No error shown. Checked errorlog.txt: See screenshot

Maybe this is is related, maybe not:
i18n_navigation.php says:

Code:

define('I18N_CACHE_FILE', 'i18n_menu_cache.xml'); # cache file in data/other

There's no such file in data/other. If I create the file manually, it is deleted on saving the menu order.