Simulink function block debugging not working

Hello,

I cannot share the code/model, but I cannot get the debugger to stop at breakpoints in function block code. Get error such as:

failed assertion in b:\matlab\src\cgir_vm\vm\nodeconverter.cpp at line 1333: In unhandledNode: Unhandled node (:): $0:$1:$3, inData(0) type: type int32_T = sint32;, inData(1) type: type int32_T = sint32;, inData(2) type: type int32_T = sint32;, output type: type _ = int32_T{col}[4]; [ 0] 0x00007fff117eb4f

Running in Normal Mode. Tried deleting .slxc and slprj files to no avail. Note that I have to close the model and reopen it to get back to the error I was working on.