Inogen, Inc. Sold a defective air machine, that has been replaced 3 times Goleta California

I'd received my first machine on 9/22/20, in a box (with pictures of the product), wrapped in shrink wrap, and delivered by FedEx. My son had to sign for it,  as i couldn't be present. There were no obvious tears or holes in the packaging. After opening the box, and removing the handbook, advertisements, power cord, and batteries, I'd pulled out the air concentrator machine, (which was also wrapped in plastic). It appeared as a never-used-before air concentrator machine.

I'd called the agent to help me get it set up, and all went well. Until 5 months later in March 2021, when the first error code ("communication "error) displayed. I called Inogen's customer service number, explained the situation,  and we worked together on trying to fix it, but to no avail. She'd said I'd have to send it back,  but not to worry,  as they'd send me a new replacement in 2 days. Seeing I had no choice, and it was covered under the warranty,  I'd agreed. When i received it, and opened it, I found only a machine in a vinyl air pillow, with a return label,  in a bare box. I didn't think much about this at the time,  as i was in need of the air,  so it was assumed it was a new machine. Returning the machine was simple, and went well.

Within a couple of weeks,  however,  the rplcmt. machine displayed a different error code, (" O2"),  and shut down within minutes after displaying. Again,  I'd called CS,  and another replacement machine order was made. Being a Friday,  however,  meant that I wouldn't have this unit until Tuesday,  of the following week,  (as they have no one in their department that issues on the weekends), regardless of urgency status. Needles to say, this time i suffered through.

The unit arrived just like the last, packed the same,  and again,  i was just grateful to have, (what i thought) another new machine. A short time later, I'd discussed with my husband, the irregularities of these machines, and he'd agreed. Are they were defective? And why aren't they packed in the same "new" sealed box? I decided to place a review on their company website. They replied with the same CS number to call to discuss. Pathetic.

Until September 2021, when again, another "O2" error code was displayed, (which means the concentrator's oxygen output is producing at a low level),  and within a couple of hours,  the unit shutdown. This is the 4th machine/3rd replacement machine,  I've had now,  within 13 months. Again,  same procedure,  same response,  only they'd changed shippers,  so now there isn't even any paper trail to show pick up, or return delivery.

Again,  I'd placed another review on their website. This time they responded with wanting to "earn back my business",  and to contact them. I called. I was told the call had been escalated,  and someone would call me back. I'm still waiting nearly a month now. And I'm getting ready to have yet another machine replacement soon,  as this 4th machine has produced yet another code. This time is for servicing. How can it be time for "servicing" a new machine of 1 month old? 

Are these machines defective? Are they refurbished?