What are you running pfsense on? When you say you replaced the modem, it really was a modem.. Or a gateway (modem/router combo) What is the model number? What upload speed to you have? Your pfsense wan is pubic IP or rfc1918?
I run uploads all the time, plex server serving up to friends and family.. I just uploaded over 45GB of stuff for just the other day for my friend..
Looks like I do over 400GB a month
[image: 1601774020482-400g.png]
Never seen an issue.. The other day when I was uploading, pretty much pegging my upload pipe for hours.. No traffic shaping, no need to really do anything at all..
So to try and figure out your issue going to need some more info. You say you start seeing packet loss, well yeah if that happens at some point pfsense is going to kill the connection on its own once it thinks its gateway is offline..
Can we see your quality graph when this happens... For example you can see here while my response time did go up while uploading that large 45GB of data.. There was no packet loss.
[image: 1601774354437-upload.png]