The Warriors have had that happen to them in this post season. Remember game 5. It was 29-28 Grizzlies with 1 minute 9 seconds left in the 1st quarter. By the end of the 1st quarter it was 38-28, at half time it was 77-50, and then 119-67 at the end of the 3rd. So the quarter scores were 38-28, 39-22, 42-17. Golden State turned around and won game six by 14 points to close out the series.
Teams can just have bad stretches. That said, there should be something that can be done to stop the bleeding, especially when in the case of the Celtics it is mostly self inflicted. I mean if Miami had come out and gone 10 of 11 from 3 or something that is one thing, but turnover after turnover, many unforced is the real issue.