ipv6 - HE tunnelbroker - high pings volatility

[GreenMatter]

I'm not sure when it started but at least for the last couple of days I see in ipv6 gateway monitoring:

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RTT: 191.5 ms
RTTd: 123.9 ms
Loss: 3.0 %
RTT used to be 15-25 ms and RTTd around 10 ms.
gif interface has same MTU as is on tunnel broker's side: 1480. gif MSS is also set as 1480 and system automatically subtracts 60b and reaches 1420. It is checked by http://pmtud.enslaves.us :

Direction	Maximum Size Segment	Client Sent MSS	Notes
Server to Client IPv4	1460	1460	OK
Client to Server IPv4	unlimited	n/a	OK
Server to Client IPv6	1420	1420	OK
Client to Server IPv6	unlimited	n/a	OK

So, is it something related to opnsense (latest 25.7.11) or more on HE tunnel broker's side?