"Sign Transaction" page don't always load XDR from the url

[fnando]

What did you do?

Tried accessing the "Sign Transaction" page with a XDR.

Even when the transaction is displayed, hitting the browser's reload button redirects without the actual xdr.

https://user-images.githubusercontent.com/3009/146447274-a013d5b5-1e62-4030-a88e-54e2ccff3af2.mp4

What did you expect to see?

The transaction that should be signed.

What did you see instead?

Sometimes the page shows the XDR, sometimes I'm redirected to https://laboratory.stellar.org/#txsigner?network=test (which doesn't include the xdr=:xdr parameter.