Question about my recent site migration and 301
Anybody have experience with what I’m seeing? 

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I migrated my site to a new aged, very strong and yes very clean domain and saw the new site take the rankings of the old site within 7-12 days of 301-ing. 
Rankings improved rapidly from days 13-17 with the new domains extra power and authority (we’re talking a big surge slightly over doubling traffic from old domain). 
All the sudden middle of day 18 (Saturday) my rankings just plummet and top 5 rankings disappear from top 100 continuing the decline into today. 
Quality long form quality content. 
I don’t think it’s BERT but I’m not 100% sure. 
Site is still holding some featured snippets so a bad domain isn’t in play (I also know the history is clean). 
Is a dance like this typical
after 301-ing? The initial traffic surge seemed odd to me and too fast for how google works these days, but maybe that’s normal?
Could it be dancing because of BERT? (I’ve not heard of others seeing this but know it’s typical with updates)
So many factors at play but does anyone have any thoughts or experience with this?
You used webmaster console site moving tool?
Have you implemented this correctly on all levels? If so, give it a week. 301 is fine.
This is normal 301 lasts for few days and then it’s gone, that’s why I don’t like 301 now you’ll need to build some backlinks powerful ones and then you’ll recover again.
Yes, done 301 correctly on all levels, page by page and in GSC. I’ve done many successful 301s and never seen this rapid growth and the drop a few days later. 

Normal? 301 is suppose to pass juice permanently, no?
BERT is the latest google update they announced last week

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