What can cause a SIGSEGV # 11? Is it normally attributed to one issue? Is there a way to tell kdenlive to ignore a SIGSEGV rather than terminating?

Signal 11 is segmentation fault. This means the program is trying to access memory (or I/O ports) it doesn't have permission for. This is to prevent applications from messing up other applications or even the operating system. The signal can be "caught" and "ignored", but most of the time that won't buy you much, because it really indicates a serious error that the application cannot recover from.

The most common cause for a segmentation fault is simply a bug in the application, dereferencing a null pointer being favorite. Far less common causes are: dynamic library version mis-matches, overheating of the cpu and kernel bugs. But as said, most of the time it's simply a bug.