I have a Freeform Pro standard (non-composer) form. I cannot reproduce the issue, but I have gotten a report of this error: "Invalid form id(s) submitted".

Secure forms is already turned off for this site, so we can rule out XID issues. My form tag looks like this:

{exp:freeform:form
  form_id="3"
  required="lastname|firstname|address|city|state|zip|phone_number"
  form:class="freeform"
  inline_errors="yes"
  return="{current_url}"
}

Yes, there is a form with an ID of 3 in the system. I have been able to submit the form myself with no issue.

Most of my research on this error reveals that it's either an XID or htaccess issue. But I don't think either of those apply in my case, since the form works most of the time, and since secure forms are turned off. What other reasons would this error occur?

EE 2.5.5 Freeform Pro 4.0.12

There is no budget for upgrading EE.

I have a Freeform Pro standard (non-composer) form. I cannot reproduce the issue, but I have gotten a report of this error: "Invalid form id(s) submitted".

Secure forms is already turned off for this site, so we can rule out XID issues. My form tag looks like this:

{exp:freeform:form
  form_id="3"
  required="lastname|firstname|address|city|state|zip|phone_number"
  form:class="freeform"
  inline_errors="yes"
  return="{current_url}"
}

Yes, there is a form with an ID of 3 in the system. I have been able to submit the form myself with no issue.

Most of my research on this error reveals that it's either an XID or htaccess issue. But I don't think either of those apply in my case, since the form works most of the time, and since secure forms are turned off. What other reasons would this error occur?

EE 2.5.5 Freeform Pro 4.0.12

There is no budget for upgrading EE.

EDIT: There's also no caching on this form, no tag caching, no CE Caching, no Stash caching.