Theme inner field collection field(s)
What you're experiencing is a bug. It happens quite often with contributed code, since it usually moves faster than it is tested. But don't worry, being contributed also means there are lots of people using, and probably someone else will bump into the same issue as you are experiencing.

When you face an issue that looks like a bug, you should ask yourself whether you've configured everything properly. Check first, but if there's nothing obviously wrong, give the issue queue a visit. Every module, theme or profile has an issue queue where people report bugs, suggest features and ask for support.

Search the issue queue and you may find a patch to your issue. If there is no report of your bug, file a new issue and provide a step-by-step guide to reproduce the error. That means you will have to try installing and configuring the module again on a fresh Drupal install. When the module mantainer sees the bug report, the steps to reproduce will make it a lot easier to debug and provide you with a fresh patch.

Mantaining modules/themes are usually voluntary work, and if you don't provide the steps to reproduce nor reply to mantainer questions, your issue will probably be postponed. Get involved with the community, it pays off.