Kourtney Hause grabbed a second-half winner, with Bruno Fernandes missing a 93rd minute penalty.
Solskjaer said, "Obviously disappointed because the goal is offside. It's unfortunate to have that decision against you."
On three defeats in last four games in League and Cup, the manager added: "When you lose games it's a concern of course it is."
On Fernandes' missed penalty, Solskjaer said: "First of all the way they get round the penalty spot, get round Bruno and that, that's not to my liking. Bruno is usually very good in those positions and unfortunately he missed this one.
"It doesn't get in Bruno's head. He's strong mentally and he'll step forward again. The decision (on who takes penalties) is made before the game."
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