IPv6 tunnel fragmentation and loss?

Question

Computer networks

The behavior is similar on HE and 6rd tunnels, under all clients
of the mtu interface 1280, 1280
Rakes are distributed via RD with defragmentation on remote hops (in particular, Google and Yandex), and tcp pulls out even without clamp, icmpv6 and udp drops - without being defragmented

3. 2001:470:0:11e::1 0.1% 2479 31.5 30.1 27.1 46.7 3.7
4. 2001:470:0:2f7::1 0.3% 2479 52.5 52.5 46.5 121.2 8.1
5. % 2479 48.7 48.2 46.9 108.9 4.2
6. 2A02: 6B8: 0: 0: 1800 :: 2 0.3% 2478 59.7 51.1 50.1 100.0 3.4
7. 2A02: 6B8: 0: 1800 :: 1 0.1% 2478 51.1 50.6 50.0 76.6 1.8
8. 2A02 :6b8::3 0.0% 2562 51.1 50.4 49.9 63.0 1.2

ping6 -s 1652 2001:470:0:2f7::1
PING 2001:470:0:2f7::1(2001:470:0:2f7::1) 1652 data bytes
1660 bytes from 2001:470:0:2f7::1: icmp_seq=1 ttl=61 time=63.1 ms
1660 bytes from 2001:470:0:2f7::1: icmp_seq=2 ttl=61 time=48.4 ms

ping6 -s 1452 2001:7f8::33b6:0:1
PING 2001:7f8::33b6:0:1( 2001:7f8::33b6:0:1) 1452 data bytes
^C
--- 2001:7f8::33b6:0:1 ping statistics ---
6 packets transmitted, 0 received, 100% packet loss, time 5016ms

ping6 ya .ru -s 1232
PING ya.ru(www.yandex.ru) 1232 data bytes
1240 bytes from www.yandex.ru: icmp_seq=1 ttl=59 time=50.6 ms
1240 bytes from www.yandex.ru: icmp_seq=2 ttl=59 time=51.6 ms
1240 bytes from www.yandex.ru: icmp_seq=3 ttl=59 time=51.3 ms
^C
--- ya.ru ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 50.689/51.253/51.679/0.415 ms

ping6 ya.ru -s 1233
PING ya.ru(www.yandex.ru) 1233 data bytes
From www.yandex.ru icmp_seq=1 Time exceeded: Defragmentation failure
From www.yandex.ru icmp_seq=2 Time exceeded: Defragmentation failure
From www.yandex.ru icmp_seq=127 Time exceeded: Defragmentation failure
^C
--- ya.ru ping statistics ---
187 packets transmitted, 0 received, +127 errors, 100% packet loss, time 186237ms Any

thoughts?