I’ve engraved on eggs (very uneven curved surface) and grains of rice (even more curved surface) and the secret to getting a good text engrave on anything, since text is perfectly horizontal, is to make sure that the item you are engraving on is completely square to the laser head.
I cut a collection of spacer sticks that butt up against the front of the machine, and align whatever I’m engraving against one and tape it in place. Then size the text to fit on it.
It’s not 100%, but it does cut down on a lot of errors introduced by having the item canted on the tray.
(Might work in this case too - the laser is going to engrave straight down, as long as the object is square, you’ve got a better chance that the text will stay on the object)
The thickness of the material is absolutely critical for placement though. Use an average thickness number, and be sure to enter that into the Unknown Materials slot, or it can miss the item completely.