Eagle warriors with cloaks of invisibility

So my group of friends and I are still playing aoe2 HD because one of them has a second rate PC (I don't blame him, he is a peasant from Manduria in southern Italy with a troubled past and a rather dysfunctional family).

But I have a problem: I can't see eagle warriors. They are invisible most of the time and become visible only intermittently. This happened to me in multiplayer games but also in the scenario editor. Have a look at this video:

https://streamable.com/r82q6

Any suggestions on how to solve this issue?