Dunno but ..
https://docs.moodle.org/dev/YUI
clip from above:
"Note: As of Moodle 2.9 we are transitioning away from YUI to AMD modules and JQuery"
Hmmmmmm ... let's see ..."core_yuimodule" looks like that theme is using YUI libraries ... so let's see:
In config.php set the theme to something other than lamba - like clean or more.
Purge the cache ... does it still 'crash'? What does 'crash' look like?
Once you've identified it is the lamba theme, think posting the problem in the themes forum OR contact the makers of the lamba theme for assistance would be appropriate action.
'spirit of sharing', Ken