In a stop-start first half, the Stormers failed to get on top of their opponents, entering the break with a skamele 19-10 lead.
Afterwards, Fleck said: “Obviously [we’re] pretty frustrated with the first-half performance.
“We were looking for a bit of continuity and momentum... every time they turned over the ball, we turned it over and there were just too many mistakes from our side.
“Credit to them, they stretched us defensively in that first half.”
The Stormers had their build-up disrupted when both Frans Malherbe and Eben Etzebeth had to withdraw from the match because of flu.
It disrupted their rhythm in the pack, but Fleck’s charges stormed back in the second half to end with a respectable scoreline.
He adds: “We had a good chat at half time - [and it went] a little bit better in the second half, [but it’s still] not what we were looking for.
“We’ve been speaking about it all week - building momentum from last week...
“We won the game at the end with 50 points, but we’re not happy."