2019 Prius Slow Coolant Leak

A couple years ago my Prius was leaking coolant. I took it to the dealership and paid them for diagnostics and they said I needed a $1500 Catalytic Converter. My buddy said that was a known issue and he did the bypass for me. A couple months ago my coolant started leaking again. I found out about the TSB from September 2019 (T-SB-0135-19) on the NHTSA government website about the coolant leak issue and called Toyota Corporate and complained and managed to get them to replace the pipe under warranty even though it was over the mileage for the warranty. I thought that would fix the issue but later on that day the coolant reservoir was empty. I put some coolant in and took it in the next morning. The looked it over and said everything was fine and there was probably air in the line. However, after I left I had to put coolant in around every 4-5 days. I took it back and they did a pressure test and they said it passed. They tried swapping the caps between the two different coolant reservoirs. It was fine for about a week then I had to put coolant in again. I ordered a new coolant cap just to try it to see if it might help and they said it would be here tomorrow. I had them change the spark plugs when they had it the other day for the coolant pressure test and they sent me a photo of them. It did look like one of them was a lot whiter than the others but I mentioned it and they didn’t seem concerned. One suggestion I saw online was to get an inexpensive block tester kit (chemical fluid test) to check the coolant reservoir for the presence of exhaust gases. I haven’t tried that yet. I’m not getting any check engine codes or smoke coming out of the exhaust. They said since they replaced the entire heat exchanger pipe with the new part in the TSB that probably isn’t the issue. Since there aren’t any check engine codes I could probably just keep running it and checking the coolant to make sure it isn’t low but I’d rather find the problem and solve it if possible. I did notice when I use the funnel to pour in coolant it seems to leak out the top a little bit by the plastic piece that sticks out with the little black end on it. I think that’s the overflow but I’m not sure. I might not be using the correct funnel.

Does anyone have any ideas on what else to check?