Having dealt with a flare a few days after an endoscopy earlier this year, I think one could include the possibility that some stomach fluid could have made its way into your lungs. This was speculation in my case. A week’s rx of amox-clav cleared it up for me but the inflammation/irritation took awhile to calm down and did affect my 02 levels. so, I am in a pulmonary rehab program that is improving my 02 level especially during exercise and sleep. My MAC, diagnosed and treated in 2012 with the “big three,” settled in my right upper lobe predominantly but recently a nodule appeared in my right middle lobe. I am due for another CT scan in a couple of months. I posted more detail here to encourage those undergoing treatment that, as awful as some of the side effects are, for me they made the difference for which I am grateful. Daily exercise, sleeping with the head of my bed elevated, and reducing my carbohydrates and continuing to be followed by a pulmonologist has helped very much the last 12 years. I wear a mask while gardening and while in stores and other crowded places and have faithfully gotten inoculations for flu, Covid and RSV.