Need help isolating issue with downloads

When I try downloading large files in chrome or edge (iso files, or even large-ish pdfs), I get a network error message and have to hit the resume download button multiple times before I can get the whole file. This was happening across multiple computers on my network. I tried troubleshooting and went to my linux box to try via command line.

curl: (56) OpenSSL SSL_read: OpenSSL/3.0.18: error:0A000119:SSL routines::decryption failed or bad record mac, errno 0

Then I logged into my router's console directly (Ubiquiti UDM) to try isolating where it was happening, and I got almost the same curl error.

curl: (56) OpenSSL SSL_read: error:1408F119:SSL routines::ssl3_get_record: decryption failed or bad record mac, errno 0

It seems to be a TLS handshake error (not really sure, but that's what I get from google).

I tried checking MTU on my Verizon 5G gateway and router, and they are both set to 1500 (since this was one thing I found from googling), and the 5G gateway is in IP passthrough mode (bridge mode). My ping to 8.8.8.8 seems to be solid, so I don't think it's an intermittent network drop. I can't seem to find anything on the unifi logs that indicate a problem, but I'm not really sure what to look for at this point. I tried going through the 5G gateway logs, and I couldn't tell or find anything that stood out other than the 1 minute lease renewal, which seems to be standard for cellular based internet. I rebooted ALL the devices, too.

I'm kind of stumped from here and don't know how to troubleshoot any further. Could the UniFi IPS/IDS be causing problems here (no security entries are flagged in the UniFi logs)? Could the UniFi Ad Block cause a problem here? I'm not using any VPN, and all my firewall settings are factory default.