YouTube Thumbnails problem. (not loading)

[mysz0n]

Do you have any reports from your customers about not loading youtube thumbnails?
The problem occurs on 3 different Internet providers plus two different exchange points.
Sometimes the thumbnails will not load at all, sometimes it works without a problem.
I changed DNSs to google (and other) , I updated all MT.
BGP and pppoe servers are working on CCR, with fresh installation of 6.42.10 package (installed with netinstal)

If you do not see the thumbnail and click on it - the movie normally turns on. It does not matter which browser you use.
All attempts to solve the problem help for a while (change to external IP, clearing the cache, etc.)
Sometimes it’s just that on the TV the thumbnails do not load, and the phone works. Suddenly, the phone stops working.
The problem occurs with many customers on various devices, this is not an individual problem.
I do not have ideas anymore.
Please help

[flynno]

Have you tried using a mangle rule for MTU

/ip firewall mangle add chain=forward out-interface=pppoe-out1 protocol=tcp tcp-mss=1440-65535 tcp-flags=syn action=change-mss new-mss=1440 passthrough=yes
/ip firewall mangle add chain=forward in-interface=pppoe-out1 protocol=tcp tcp-mss=1440-65535 tcp-flags=syn action=change-mss new-mss=1440 passthrough=yes

in-interface=pppoe-out1 enter WAN interface
tcp-mss=1440 Find MSS on this site https://www.speedguide.net/analyzer.php and change 1440 if required.

It’s possible you might have a private IP conflict with another user on the network.
Can you ping 8.8.4.4 or ping youtube.com and then try ping google.com