Does anyone else have big problems with Firefox preview? It used to work absolutely fine for me then a couple of months ago it just started crashing every time I tried to open a website. This includes sites and pages that had previously loaded with no problem at all. It has become pretty much unusable for me. And this is on two different devices by completely different manufacturers :-(
It crashes for me too. I can deal with that. I find it much more annoying when it loses my tabs that I keep open to read later.
After the last update the "undo" notification at the bottom sometimes doesn't disappear, which is annoyingly placed over the address bar and menu button. There's also no way to manually dismiss the "undo" notification.
Despite all this it has by far the nicest user experience of an Android browser so I stick with it in the hopes one day it won't be super buggy. I'm sure that day will come.
Have you tried raising a bug on their issue tracker? I had the opposite experience. It was a bit unstable about 3-4 months ago where some websites would make it crash but I haven't faced any crashes in the last few months and it looks close to being a finished product.
It crashes sometimes (about twice a week for me), but it's Preview Nightly what I use. I would suggest you uninstall and reinstall (from Google Play). Maybe it helps.