Priv limited download speed on 4G

I'm having some weird behavior with my Priv. The download speed when I'm connected to 4g is around 3 Mbps, if I set the network to only connect to 3g I get around 8 Mbps.

I thought it was a problem with my carrier, then I switched my SIM to the Passport, and I get 30 Mbps on 4g.

Any ideas about what it could be?

The Passport is SQW100-4 and the Priv is SQV100-3, so both supports the same frequencies.

I contacted the carrier and they said it was all ok on their end.

Also, if a put my SIM in the Passport, and connect the Priv to my Passport's wi-fi router I get 38 Mbps down and 12 Mbps up.

What the hell am I missing?