core: Unable to serialize to JSON. Bad data found at $.event.result

The problem

using a frontend template card always worked, but since the new json in todays dev throws 2 errors. one on core.entity_registry, and this in the template below

What version of Home Assistant Core has the issue?

2022.7.0.dev20220623

What was the last working version of Home Assistant Core?

2022.7.0.dev20220622

What type of installation are you running?

Home Assistant OS

Integration causing the issue

template websocket

Link to integration documentation on our website

https://next.home-assistant.io/integrations/template https://www.home-assistant.io/integrations/websocket_api/

Diagnostics information

No response

Example YAML snippet

{%- for s in states.binary_sensor -%}
                {%- if s.object_id.endswith("firmware_update") and states(s.entity_id) == 'on' -%}
                    {{
                      { 'type': 'custom:template-entity-row',
                        'entity': "button." + s.object_id.replace("firmware_update", "ota_update"),
                        'state': 'BUTTON',
                        'secondary': state_attr(s.entity_id, 'installed_version')

                      }
                    }},
                {%- endif -%}
              {%- endfor -%}

Anything in the logs that might be useful for us?

Logger: homeassistant.components.websocket_api.messages
Source: components/websocket_api/messages.py:199 
Integration: Home Assistant WebSocket API (documentation, issues) 
First occurred: 08:46:38 (2 occurrences) 
Last logged: 08:46:40

Unable to serialize to JSON. Bad data found at $.event.result={'type': 'custom:template-entity-row', 'entity': 'button.symfonisk_dining_ota_update', 'state': 'BUTTON', 'secondary': '20211109-130223/v1.11.7-g682a0db'},{'type': 'custom:template-entity-row', 'entity': 'button.tester_ota_update', 'state': 'BUTTON', 'secondary': '20211109-130223/v1.11.7-g682a0db'},(<class 'homeassistant.helpers.template.TupleWrapper'>

Additional information

see also https://github.com/home-assistant/core/issues/73882