It's going to remain a mystery if you don't share any more details. Not sure if I'm doing something wrong, but that graph doesn't even open for me.

After several google updates, serp jumping is a common thing. You should check your website backlinks immediately. Remove any "Broken" and "Bad Links".

Well this is first time i see that much jumping and still jump like that every day and just for that one website... I have even one ranked still on first spots where are more then half links deleted... and this one...

Have you manually confirmed these rankings?

Sometimes when you see a drop like that it is the rank checker that is wrong. I used to see that a lot when I used SERPFox. There were days where I think they burned out their proxies. Instead of finding my first listing in the SERP, they would find a secondary listing way back outside the top 8 pages or so. Then the next day when they rank checking was working properly, they would find my first listing right where it always was.

It could also be from a lot of newer low quality/authority links being crawled & Google trying to calculate a new SERP position.

I've not seen this kind of variation, but changes to contents or site structure are also a potential reason.

For example, a page was previously linked form main navi or a strong page, but was dropped after a site reorganisation. Google doesn't see the strong internal links any more, and takes that as a signal that the content isn't important to the site owner.

... and now we've pinpointed the problem to just about anything on or off site, or in the tracking setup.

Well, im not new with SEO, serps tracker isnt problem becose i chk it manual to.. even with my IP and from USA server ip. I understand that google put it on 170 position becose of something but why he bring it back on position 5-10 after few days... 3 times already... I dint change anything on page... Im doing some authority high pr links but realy slow... maybe just that is problem but ... I dont know...