I was once told that insiders sell for many reasons and buy for only one reason. The lesson being that insider sales shouldn't be a huge consideration.
But it is hard to not read into this, quite a bit.
If a plurality of "insiders" have sold 50% of their stock then you can be sure the company is on shaky ground. What they've just done is cashed-in to cover any downside losses and perhaps make some money. They're still invested to make more money if there's an upside swing. What all this tells you is Tesla is not a 'Buy' stock.
But it is hard to not read into this, quite a bit.