Invalid text character, restoredefaultpath doesn't even work

Hi all -

I've broken one of my iterations of Matlab and I really don't know how. I can't close the window because it gives me this error:

Attempt to execute SCRIPT builtin as a function:
C:\Program Files\MATLAB\R2018b\mcr\toolbox\matlab\lang\builtin.m

If I try to restoredefaultpath it gives me this error:

Error: File: restoredefaultpath.m Line: 1 Column: 25
Invalid text character. Check for unsupported symbol, invisible character, or pasting of
non-ASCII characters.

Thankfully this isn't currently the end of the world because I can run up to four iterations on my machine. But I really want to fix this!

Thank you!