A reliable Fix:
I've seen many beginners successfully ignore overthinking by naturally being competitively intense. To have your mind occupied with technique while playing a match it means to me that a player needs to learn to focus. Heightened intensity is where your mind has no room for technical concerns.
At an intermediate playing level you need a weapon that won't break down. I'd pick one and work on it until it becomes highly capable of direction, depth, spin, and then speed. The forehand is usually the best stroke for this project. At that point you can implement strategy and forget worrying about form while playing. The other strokes will follow.
Do you need an example of intensity to emulate. Think Rafa Nadal