Phantom breakpoint in MATLAB Function block

MATLAB 2017b. I have a simulink model with a MATLAB Function block in it. There are no breakpoints set in the MATLAB function code in that block, but when I run the model, execution always stops on the same two lines, just as if I had set breakpoints at them. I want to get rid of these phantom breakpoints. How can I do that?

Here's what I see when the code execution stops:

Here's what I've tried so far to solve the problem:

1. dbclear all
2. dbstatus (which shows no breakpoints set)
3. deleting slprj directory
4. setting and unsetting breakpoints on the affected lines
5. enabling and disabling breakpoints on the affected lines

I am not an expert in simulink debugging, other than the basics, so perhaps I am missing something obvious or used the above commands wrongly.