Hi,
With Finnish language in use, in libs/formslib.php, form_init_date_js() has several calls to strtotime. They can return results in latin1 encoding if locales-all is installed. This breaks js_writer::function_call with json_encode not checking error status.
This results in for example /course/edit.php?id=2 breaking such that the detailed settings boxes cannot be expanded at all.
This reproduces in Moodle 3.3/PHP 5.4 and 3.5/PHP 7 on Debian 9/stretch.
Removing debian package locales-all fixes this issue, but should probably be taken into account in Moodle?
Sorry I may not have the time to properly report this, but here's hoping a quick forum message has value. I'll try to keep tabs on this thread if you need more info.
Olli