Chris Boyd's side put the Bears to the sword at Ashton Gate, securing a bonus-point 36-20 Gallagher Premiership success.
The foundation of that win was the scrum as Saints won a huge amount of penalties, particularly on Bristol ball.
And Lam said: "There was a lot of good stuff but ultimately our scrum didn't function and we couldn't get into the game.
"We got penalised on our ball and we couldn't launch so it ended up being a very slow game.
"We started well and we had lots of opportunities to score but we didn't take them.
"We ended up going down 20-13 and got a good try at the start of the second half but we just couldn't get into it after that.
"We got penalised and there were turnovers."
On the scrum struggles, Lam said: "We've got to go and have a look at it.
"We're obviously missing a bit of firepower and we lost Max (Lahiff), who felt his shoulder after a scrum.
"We'll go back and we'll look at it.
"The beauty about having a system is that you can work on it.
"It's been a long time since we've been in a game where our scrum has been that dominated.
"It hurts but we'll go back and fix it."
When asked whether there were any positives from the Bristol performance, Lam said: "Ultimately we're trying to improve our attack and there was some good stuff.
"There was some really good contact in our defence.
"We had long periods of time where we didn't have any ball but the biggest thing for us is to sort that scrum out because then we can stop losing territory and points."