they did change the backend.. it COULD be script(s). In the old engine, some scripts ran terribly in the old backend. You could disable all script real quick and make a test order and see if it works OK and start adding them back till it tanks and you can identify the issue (if its a script)

Scripts will still run on the old engine unless the specifically say 2.1 jsdoc. 2.x is still treated as 2.0 until 2.1 comes out of beta.

yeah thats my bad i've had it on the brain lately ... still a worthwhile experiment if you're having some issues still