Research, Interrupted

I've found that my current research project is abruptly deselected, is no longer available for selection, and I'm required to choose a new research project. This has happened upon a couple of key research projects:

1. Orbital ship assembly (Medium hulls) disappears, and I had to research Large Hull Construction before it re-appears as an option.
2. Carrier disappears, and I'm now trudging through Planetary Defense Dome.

I suspect what has happened is that I've traded tech such that the game has made a decision that my current research project is no longer allowed. I can find a save game to demonstrate if this will be useful.

However I don't think this is a sensible dynamic which essentially means that during times of critical research, players stop trading tech. So if this is intention, can it be disabled, or some kind of a warning displayed? I've no idea what the criteria for kicking out my current research project is, nor do I care for having to switch between the tech tree and the trading screen to establish whether a proposed deal will mess up my research. So if this feature is intended, and is here to stay, then a warning please.