I'm investigating a strange issue in our network thats related to connections seemingly dropping out. I.e. downloading a large file it will just outright fail at some point
This seems to predominantly affect international traffic, but that may be related to the fact it takes longer to complete

One thing that may or may not be related, looking at one of our main datacenter routers I noticed that if I run '/ip firewall connection print count-only interval=0.2s' I notice quite a dramatic drop in connection count every 5s. It'll go from ~190,000 to ~165,000, increment back up again and repeat this cycle over and over. This seems like an excessive number of dropped connections
Is there a known issue with this number of connections on a mikrotik router? Or any commonly overlooked configuration issues I should be looking at

This particular router does have connection tracking enabled, and perhaps it shouldn't. It handles some NAT so for the moment its been left enabled. I'm wondering if this is an issue, even though it states maximum connections is approx 1m so i'm nowhere near the connection limit

I don't think this is related to number of connections (could still be wrong though)
I converted the router to not need TCP tracking and moved the NAT functionality elsewhere. Problem still exists, TCP connections are dying

It's similar to some threads i've managed to come across, except adjust connection values on every router between customer and DC has still made absolutely no difference

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viewtopic.php?t=168452

I'm stumped, no idea what to do here. Have confirmed a 1500 byte packet can go in both directions successfully, doesn't appear to be MTU related, despite that using 1400 byte L3MTU helps (a bit, not entirely). It does seem to be less drastic at nighttime when its quiet, during the day it was causing large downloads to fail in ~30s-15m but its night time right now and it can go for much longer before it fails. RDP sessions are still dying but downloads tend to go longer