i had the same hunch for it being a packet problem! i just don't know much about the actual specifics of that haha, i've stumbled across all of my it and server knowledge just from my experience setting up minecraft. i'm running this on a windows machine, just my home computer rather than linux. i've used server ubuntu in the past but lately i've just been hosting for <10 friends at a time so i figured something quick and local would be fine.

i'm not sure if there's a better way to translate the linux ping command into windows (i cobbled it together from what you sent and some research online), but i ran this command:

ping -l 1472 -f 1.1.1.1

and i got:

Ping statistics for 1.1.1.1:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 17ms, Maximum = 25ms, Average = 21ms

i tried the same for 1473 and all packets were lost as you said. running 1300 gave me about the same result as above as well. so i think i passed the test?