I'd be baffled as well. Have you tried a different USB stick? Might be wonky, but I've never had that issue, I've just heard of others. I chose Elegoo as my first printer and have never looked back. I love the Saturn 3. Maybe one day might try the 3Ultra. Elegoo have released the Saturn 4 and 4 Ultra , but not enough features to upgrade this time. It has some nice features, but the build plate is a bit smaller than the 4 so not interested. I actually just found a heater and ordered it to have it arrive today. Will set it up in a bit and see if the prints are even better.
https://www.amazon.ca/dp/B0BL6WZPM9?psc=1&ref=ppx_yo2ov_dt_b_product_details
Elegoo has the most incredible customer support also and I have been nothing but impressed with their products. Since my journey has begun in 3D printing I have bought the Mars 2 Pro, Saturn, Saturn S, Saturn 2, and now use the Saturn 3. For FDM I started on the Neptune 2, Neptune 3, 3Pro, and 4Max. Currently I use 3 printers, the Neptune 3 Pro and 4Max, and Saturn 3. I use Siryatech Navy Grey ABS like resin which is very fine and provides exceptional detail and strength. I have some clear Syryatech Ble which hopefully will make printing clear parts easy.
I guess this is a long rambling post to say I love Elegoo and have not heard a lot of good about Phrozen.
James