Just a follow up here: I'm not able to replicate this on my end. The Widget updates every 5 minutes as expected. My Windows display is running Chrome App Player, on Chrome 44.0.2403.107, using the default layout for the Spreadsheet Widget. Are you by chance using a Custom Layout?
I am running the same version of Chrome you are with the Default Layout. After the issues I had previously with custom layouts, I'm not going that route again.
After testing again this morning. It's now working as expected again. Not sure what changed since Friday, but I tried multiple times with restarts and republishing in between to try and get it to trigger.