Version: Odoov12 on a test server.

I got the following error when I loaded the shop (product pages work fine):

maximum recursion depth exceeded in comparison
Traceback (most recent call last):   File "/opt/odoo-test-12/odoo-server/odoo/addons/base/models/qweb.py", line 346, in _compiled_fn
    return compiled(self, append, new, options, log)
  File "<template>", line 1, in template_website_sale_search_5986
  File "/opt/odoo-test-12/odoo-server/addons/website/controllers/main.py", line 43, in __call__
    path_args = OrderedSet(path_args or []) | self.path_args
  File "/usr/lib/python3.5/_collections_abc.py", line 424, in __or__
    if not isinstance(other, Iterable):
  File "/usr/lib/python3.5/abc.py", line 182, in __instancecheck__
    if subclass in cls._abc_cache:
  File "/usr/lib/python3.5/_weakrefset.py", line 75, in __contains__
    return wr in self.data
RecursionError: maximum recursion depth exceeded in comparison

Error to render compiling AST
RecursionError: maximum recursion depth exceeded in comparison
Template: website_sale.search
Path: /templates/t/form
Node: <form t-att-action="keep('/shop'+ ('/category/'+slug(category)) if category else None, search=0)" method="get" t-att-class="_classes">
            <t t-if="attrib_values">
                <t t-foreach="attrib_values" t-as="a">
                    <input type="hidden" name="attrib" t-att-value="'%s-%s' % (a[0], a[1])" data-oe-field="arch" data-oe-xpath="/t[1]/form[1]/t[1]/t[1]/input[1]" data-oe-model="ir.ui.view" data-oe-id="932"/>
                </t>
            </t>
            <t t-call="website.website_search_box"/>
        </form>

The error occured while rendering the template website_sale.search and evaluating the following expression: <form t-att-action="keep('/shop'+ ('/category/'+slug(category)) if category else None, search=0)" method="get" t-att-class="_classes"> <t t-if="attrib_values"> <t t-foreach="attrib_values" t-as="a"> <input type="hidden" name="attrib" t-att-value="'%s-%s' % (a[0], a[1])" data-oe-field="arch" data-oe-xpath="/t[1]/form[1]/t[1]/t[1]/input[1]" data-oe-model="ir.ui.view" data-oe-id="932"/> </t> </t> <t t-call="website.website_search_box"/> </form>

  File "/opt/odoo-test-12/odoo-server/odoo/addons/base/models/qweb.py", line 346, in _compiled_fn
    return compiled(self, append, new, options, log)
  File "<template>", line 1, in template_website_sale_sort_6097
  File "<template>", line 2, in body_call_content_6096
  File "/opt/odoo-test-12/odoo-server/odoo/addons/base/models/qweb.py", line 348, in _compiled_fn
    raise e

The above keeps repeats in the Traceback around 200-300 times.

Factory resetting 'website.sale_search' (as the error page suggested) didn't help.

Any and all help is much appreciated!