If we activate on a SharePoint List "Allow management of content types" and use the List/Library in a non-default display langauge (Use language packs for sharepoint) then we get an "Object reference not set to an instance of an object" error during Add/Update/Delete a list entry with a K2 Form.

This only happens when the default Language for the site is for example english and the User Personal Language Preference is e.g. German.

When changing the User Personal Language Preference to English, the issue does not occur and the List Forms function correctly.

When changing the User Personal Language Preference back to German, the issue returns.

When deactivating the content types (set "Allow management of content types" to no in the list) the issue does not occur.

Reason: At this time using a non-default Display Language in SharePoint and specifically Content Types in non-default Language is an unsupported scenario for K2 for SharePoint integration. This is due to how the SharePoint API presents the List/Library details differently, based on the display language.

In my opinion this would be a very useful feature because K2 is used in a lot of different countries/languages in combination with SharePoint and so this will be a common scenario.