Module Builder - Custom NON-hidden Guid fields generates unhandled exception when clicking Backend screens tweaks link
Steps to reproduce problem
1. Add a custom field of type Guid but do not make it hidden.
2. Click the Backend screens tweaks link
Deleting the custom field got rid of the error.
What you have found is a serious bug and I have logged it as a PITS issue so that you can vote for it to increase its priority and track its progress. Thank you for bringint this to my attention.
We will try to fix this as soon as possible but till then the simplest workaround is to create your module without GUID field, edit the backend screen tweaks the way you want them and after that add the GUID field.
All the best,
the Telerik team