It’s not unusual for the placement to be off by up to 1/4" at the edges of the bed right now…they are still working on improving the algorithm that adjusts for visual placement. To reduce the issue, make sure you have the correct material thickness entered into the Unknown Materials slot if you are using anything other than Proofgrade Material with it’s pre-coded value.
As far as the Glowforge taking that long to calibrate…if it happens once in a while that can be put down to temporary WiFi signal issues, but if it happens consistently, you might want to consider running through the checklist to make sure that your WiFi signal is strong enough. They have a list of suggestions to improve the signal in the Troubleshooting section, and Pip outlined them here: