The "Tribes of the East" campaign in Heroes 5 freezes.

Have you tried skipping the video immediately after it loads? I read somewhere that there's a bug related to this. Actually, there can be glitches with the built-in video in Heroes.

Then, I downloaded all available patches, installed the original version, and applied the patches... but there was no reaction.

And I didn't quite understand this phrase... The add-on is a separate game and doesn't depend on the two previous parts, and there haven't been any patches for it yet.