I am a tech lead in a software development team (but our team is not very hierarchical - I just help with organisational tasks more than other team members do). I recently had a technical discussion with a colleague that I found overwhelming. They had done some investigation, and I wanted to get the gist of it before it was brought to the rest of the team. I had a very hard time understanding them. I am reasonably familiar with the code they were looking at, but it felt as if they were giving huge amounts of information without very much structure, and it was difficult for me to follow their reasoning. We went back and forth for a long time, but eventually I had to end the conversation because I could no longer follow a train of thought. In the end I had to more or less reproduce their investigation myself before the high level picture became clear.
This experience was very disturbing to me - I hate not being able to understand what someone is getting at, and I felt very frustrated with the conversation. Worst of all, I didn't feel able to articulate the problem until long after the discussion was over, because I didn't feel able to say "I have discussed the issue with X, but I still have no idea what the high level picture is". So I couldn't really ask for help from my manager, and I feel stupid for being unable to salvage something useful from the discussion. If it were as simple as the colleague being unclear, then I feel like I would have been able to stop them at the beginning and say exactly what was unclear in my own words. But in this case I couldn't tell what they were saying was irrelevant until I already understood the problem completely.
I am not sure how to handle this kind of discussion. I want to speak to my manager about it, but I don't know what to tell him. I could just say this colleague is a bad communicator and leave it at that, but I still have to work with them. And what if it's not their communication, and I'm just bad at understanding their investigation? I doubt it, because I don't usually struggle with technical discussions, but it is rare for me to so completely freeze like this, and it makes me doubt myself. After over 2 hours I just couldn't continue, and I lost my train of thought completely. But I felt guilty for wasting the time, and unable to explain it to my manager and move onto something else.