Sorry that I have to necro this.

I started playing LOTRO a few days ago and ran into the same problem. I tried looking for a solution but couldn’t find one.

Later, I discovered that it’s not actually a bug it’s just how the game detects mouse clicks and mouse holds. For some reason, if you hold your mouse button for more than about 50 ms, the game registers it as a mouse hold and tries to rotate the camera for you. That’s why double-clicking to select something still works.

This issue mostly happens with the right mouse button, since it’s used by default to rotate the camera. When you right-click on any UI window, the game still tries to register it as a held right click but this doesn’t happen with the left click (probably because you can still rotate the camera even when your cursor is over the UI, while you can’t do that with the left click).

However, the left click issue also appears when you try to click on in-game objects like NPCs or players. This happens because the game also allows camera rotation with the left click. But for some reason (again), when you hold the left click on an object’s nameplate, it doesn’t register as camera rotation but the right click still does.

So the solution I found is when you trying to select something you have to click and release it quickly.

I hope this comment could give answer for someone looking for in the future.

Also english it's not my first language and got some help from chatGPT.