(does?) using reCaptcha as a form element breaks cTools multi-step form

Running

Core                         System (system)                                  Module  Enabled        7.15
Chaos tool suite             Chaos tools (ctools)                             Module  Enabled        7.x-1.2
Spam control                 CAPTCHA (captcha)                                Module  Enabled        7.x-1.0-beta2
Spam control                 reCAPTCHA (recaptcha)                            Module  Enabled        7.x-1.7+12-dev

I'm building a cTools multi-step form.

Normal step->step navigation works correctly in all cases except, afaict, in the case of using reCaptcha as a form element.

When a reCaptcha exists on a form step, and is successfully filled out, on submit of the form, the user's returned to the same form step rather than promoted to the next.

It's possibly a conflict amongst multiple submit handlers -- as yet that's unproven by me.

I've filed this as a bug at cTools' queue:

Use of reCaptcha in Ctools multi-step form prevents moving to next step on submit

I'd appreciate if someone with a deeper understanding of reCaptcha module might take a look there, and offer a comment as to where the problem most likely lies ...