Alliance Ipv6 PPPoE random connection dropout

Keep MTU 1450 to be safe, mss needs to be different for ipv4 and ipv6. MTU is not router specific but ISP specific. Like my current ISP works on 1480mtu. Since local ISP use Mikrotik core, mikrotik router can tell what is maximum MTU for connecting.
 
The IPv6 issue just doesn't seem to get solved. On IPv4, the connection works for days without any issues and everything is smooth but on IPv6, after sometime the connection feels slow or images take time to load randomly, browsing has this slight pause and retry to make it work. Everything feels a bit off when IPv6 is enabled whereas when it's off there are no issues as such. Anyone else facing similar issues on Alliance or any other ISP? Anyone able to solve this issue?
 
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