I had the same problem with a Toshiba SCSI CD-ROM drive. The tray mechanism had a broken component. These are the notes I made at the time:

Faulty: tray spontaneously opens and will not stay closed. Examination of tray mechanism shows that a small white cogwheel is broken and prone to coming loose from its axle. A small amount of glue was applied to hold it in place. This repair will probably have to be performed at regular intervals.

If yours has the same problem, and a refund is an option, then I recommend returning it.

Hm I would be tempted to try and repair it but if I open it up then I won't be able to return anymore in case I can't fix it myself.

It's aggravating because SCSI CDs are getting scarce and expensive, I did some extensive searching before I found this one and had high hopes as it was, well, tested. The next one up in price was over twice as expensive and in "unknown condition as-is" which usually means known broken

The fact that little parts like this are prone to breaking means that it's very important to package the drive carefully when shipping it.

The packing was relatively OK, sheet of bubble wrap around and wads of more bubble wrap all around to fill the box. It wasn't loose or rattling in the package. I'd be OK with a partial refund and trying to fix the drive afterwards. If it's a broken plastic part I could try to 3D print a replacement.

I actually have a Philips IDE drive that behaves similar. Even after disassembly and cleaning it still does how it feels like. But since it's a nice look drinve for older systems it;s a shame to be so quirky.