This has been an ongoing battle with Medtronic for me. I saw a post on here from way back that there were no bubbles when the reservoir is inserted, but later there will be small and large bubbles. That poster was told that was impossible; there is no way air can get into the resorvoir once it it attached. Well, that is just wrong.
I do all the stuff--room temp insulin, tap bubbles to the top and remove them--all Terry's tricks. And no one is going to tell me I left large bubbles in that reservoir!
A couple of years ago, I had a huge problem with this. I contacted Medtronic each time and sent the reservoirs to them for testing. I even returned another entire shipment that was having this problem and were from the same lot. It stopped happening for quite a while. Recently, it has become a problem again--just had one on Monday.
If my glucose levels get high for an unknown reason, bubbles are the first thing I check.
Personally, I think it is the product, not the users. I think there are problems with the "O" rings in tthe reservoirs. It irritates me when anyone feels it is something I caused by not "following instructions."