Not sure if the company will do this. It seems their policy is just to replace the machine with a new one when its time to upgrade.
I had a 2014 mac mini with regular hdd, it was so infuriating to use, I couldn't believe how ridiculously slow that thing was. The issue was random slowness/hiccups. That 30 sec delay sounds like what I was getting. So I plugged in an external usb3 ssd, and used that to bypass the internal hdd. Night and day difference.