Midea Air conditioner giving off weird smell when first turning on.

I have a smaller Midea window air conditioner. We have had it for only about a year and a half. When we packed it up last year for winter, we made sure any moisture was removed. Before hooking it back up last month, I cleaned the thing out as much as possible using a coil cleaner and rubbing alcohol. I got it spotless and made sure there was no trace of dirt or mold. The first few times we ran it, it ran great and smelled fresh.

Now, fast-forward to the last few weeks. Every time we start it, there is a strong vinegar-like smell for the first 10 minutes, then it subsides. We also noticed that the airflow on it has gotten weaker. We checked the filter, and that was not the issue. The only thing I could find was that some tree buds/leaves had fallen into the exterior portion. Thinking this was the issue, I sprayed the outside with AC coil cleaner again and then rinsed it out with the hose. I got it cleaned spotless again, but the issue still occurs. What could be causing this?