After some more testing I've figured out a couple more things:
- The issue is more that there's an invisible square in the upper left that blocks clicks. If you move the inventory window into the upper left, you can't click on it either. This also prevents you from for example renaming train stops ...

I've observed this issue, but only under very specific circumstances. When it happened, I was in multiplayer, and I was not the host. The host specifically tested and was able to reorder the research queue normally. When the issue happened, I was unable to move the tech being researched and the ...