Don't forget that they use the tactic of stopping the official clock just before midnight and continuing on with legistraiting!They most certainly are in session all weekend since they have until midnight tomorrow to get this done, on top of getting 8 other bills to the governor. Tomorrow they'll definitely go until midnight so stay tuned.
--Edit--
There's also some political conflict between the House and the Senate right now over a ton of stuff, which has the possibility to affect their ability to move on the gun control language in the way that its proponents would like to see reintroduced. Second to that since tomorrow is the last day of formal session, they don't have time to come back and override Gov. Baker's vetoes. This means that they need to be very deliberate in what they send him and are likely softening anything that pushes too far to an extreme.
That's been done a number of times before, so that they are "legal".