It probably means you have a function somewhere that "shadows" a built in Matlab function, i.e. that has the same name as a built in function.
Try typing "which functionname -all" (without the quotes) in the workspace.
Instead of functionname, type in one of these functions:
- strsplit
- builtin
- strjoin
If it shows more than one path for any of the functions, you know you have a duplicate function that may be causing a conflict.
