trying to edit some content, getting this error for each RelatedItems Field "RelationList" (z3c.relationfield.RelationList)
patterns.pat.select2: Failed while initializing 'select2' pattern. query function not defined for Select2 s2id_autogen1
This is how it looks
I'm having the same issue in one of my plone sites.
What conten type are you trying to edit?
Strange thing: in another computer, the same buildout, with the same packages installed, doesn't give this error.
Plone 5.1rc2 (5109)
I think my solution is nothing you can work with
I doubled all
<script> tags in the Meta-section - after clearing that, all works as expected... sorry