Ritalin LA 2x 10mg vs 1x 20mg - same dose but difference in efficacy

Due to drug shortages, my current Ritalin LA dose of 20mg once daily had to be swapped by the pharmacy for taking 2x 10mg once daily. While it’s the same dosage and it’s from the same manufacturer and everything, I’ve noticed a significant difference in the medication’s efficacy, just because I now take 2 pills instead of one. I have discussed this issue of the medication with my GP several times, as the psychiatrist who diagnosed me has released me to the GP’s care. However, all the GP said was “you probably don’t feel the efficacy anymore cuz it’s actively working and that’s why you feel like it isn’t”. So I tested this theory. I still had some leftover 20mg, as I knew I wasn’t making up what I’m feeling with the efficacy and could tell the difference, and lo and behold, I was right. I also tested it under different conditions (busy day vs relaxing day), comparing the difference between taking 1x 20mg and 2x 10mg and I could feel there’s a significant difference in focus. It could possibly be placebo and all in my head, but because I’ve tested it a couple times, I feel that this seems unlikely. Are people also experiencing what I’m experiencing with my adhd medication, and how do you deal with it? I know there is a worldwide shortage with certain adhd medications so surely, other people are also facing similar issues. Plus, dealing with medical providers can be a headache just to even get your exact prescription filled so I’d love to know other people’s experiences and how they’re similar/different to mine, as well as possible suggestions to help me manage this.