Found your thread, very useful thank you. I've been having similar (and very frustrating) issues and am convinced it is indeed a MTU issue. I use Smarty for my home broadband (rural and no land-line option), and have been having the exact same symptoms that MrHammonds describes for a couple of months. Connection is reliable and speed good and consistent, at a radio level I have good RSRP & RSRQ numbers. My normal set-up is a Meraki MG21 4G gateway paired with a MX64 firewall and a couple of MR33 APs. I also have a spare TP-Link MR600 and the problem persists when using this for testing.
At first I thought it might be a web-caching issue as once pages eventually have loaded they them seem to be ok. Video such as Netflix and Prime does not seem to be affected, but I'm assuming this is UDP and smaller packets.
Using the instructions on
https://www.tp-link.com/uk/support/faq/190/?utm_medium=select-local and
https://documentation.meraki.com/zG...nd_Troubleshooting/Troubleshooting_MTU_Issues I'm seeing 3 restricting MTU to 1358 (inc. 28 bit header).
I've tried setting the MTU via DHCP option 26, but my Windows 10 PCs just ignore that, and I don't want to force it on them individually as it would apply even when on other networks.
I can't adjust the MTU myself on the Meraki MX, but apparently support can do this for me, so I have requested this change. I'll let you all know whether this solves the issue.