No Records Returnd by datasource

[BrendanJackson]

// Provide a general summary of the issue in the Title above

I'm getting the below errors when trying to run a product import

Notice: A non well formed numeric value encountered in /srv/public_html/magmi-m2/magmi/web/progress_parser.php on line 115

Warning: session_start(): Cannot start session when headers already sent in /srv/public_html/magmi-m2/magmi/web/magmi_progress.php on line 29

Preconditions

// Provide a more detailed information about you Magento, Apache2/nginx, PHP & MySQL version
Magento 2.3, nginx, PHP 7.2, Mysql Ver 15.1 Distrib 10.3.22-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2
// Provide example CSV file to help us reproduce your issue

PRODUCT_RR_20191209-00602.xlsx

Steps to reproduce

// Provide a list of steps to reproduce this bug, include which plugins you use
// You can attach your magmi profile files stored in directory "{your Magento dir}/magmi/conf/{your profile name directory}
1.
2.
3.
ValueReplacerItemProcessor.txt
plugins.txt
Magmi_ReindexingPlugin.txt
Magmi_CSVDataSource.txt
Magmi_ConfigurableItemProcessor.txt
ImageAttributeItemProcessor.txt
DefaultValuesItemProcessor.txt
ColumnMappingItemProcessor.txt
CategoryImporter.txt

Actual result

// Tell us what happens instead - screenshot, logs etc.

1. 

I'm digging into this, for the first time today, hopefully someone else out there is a bit more familiar with it than I am though.