Error importing function definition, who faced?

Question

linux

I have a separate script with functions. It looks like this:

function som_func
{
бла бла бла
}

several functions are described in this way, and at the end of the file:
export -f som_func
everything was gorgeous and then at one moment for one of the functions it writes this:

/bin/bash: error importing function definition for `BASH_FUNC_som_func'

why - I can’t understand. everything is done the same way according to one template ...
Who came across? What could be the reasons?
ps this nonsense is only on centos5. On centos6,7 everything is fine with the same script...