So it is ND (also indicated by the name of the tool).
No, you're doing exactly the same thing MikroTik support did — that is, not reading the addresses that are being targetted. Despite using a tool for ND crashing, it is not ND which is causing the problem — it's just an easy to find tool which will send ICMPv6 packets to lots of different destination addresses.
MikroTik Support eventually read my emails properly, after a week of back-and-forth, and acknowledged this problem:
I can confirm the problem, in one case forwarding of ipv6 traffic eats all the memory. There is also another case when kernel is crashing, but also can be related to low memory.
We will look into this problem.