Calculation error: Invalid value "B-034" (string): must be number

The following code once worked in the beginning of this year, but now doesn't work anymore and always returns the following error:

Invalid value "B-034" (string): must be number

In case of this specific example, @All of Number contained the following item field values:

B-034 (Branding v1)
D-034 (Branding v1)
N-001 

The calculation code:

var arr_num = @All of Number;
var regex = /B\-\d\d\d/gi;

if (arr_num != null){

    var result = regex.exec(arr_num.join(", "));

    if (result != null){
        result.join(", ");
    }
    else{
        null;
    }

}
else{
    null;
}

Basic solution suggestions such as creating a new calc field didn't help.