Shelter of the 11 mission

[FOARP]

This is driving me crazy: it doesn't appear possible to get to the hotel before either 1) being spotted or 2) the mission being lost for some unexplained reason - it just ends with the message that the Soviets captured the hotel, but I haven't even reached the hotel so the Soviets never lost it and never needed to take it back.

From the look of it the only way to win this mission is to go in noisy and to hell with sneaking. Am I wrong about that?

[Cynicus Nihilisticus Paradoxus]

Yes, indeed it is possible albeit difficult. Proof, my stealth playthrough: https://youtu.be/rYhlVh1NjlA?si=Zv7_QLZB1ZliHVgd

First off, here is
Stealth is not a very well understood mechanic in this game from what I found out, And it takes a whole lot of practice to understand exactly what works and what doesn't and I myself am still puzzled every now and then as to why people get spotted.

However, I'm the 2 most important things are vision and noise/sound. First off, you need to use terrain to block vision to your guys, and it also helps to know more or less how far people get spotted whilst prone. As for noise, most things have a noise factor in this game, like shots fired, shells hitting the ground, engine on tanks ect. To get a little better understanding of it, look at this vid from 8:42 https://youtu.be/yOy-IpEArUw?si=5cIlSVe76YgnFptr
As I explain a little bit about how stealth works in this game

In this map, basically the only "silent" weapon you have are the knives that you can throw, they make no noise.

So you have to sneak up, throw knife, run, get body out of sight and then sneak around again. Grenades help when you have to take out multiple enemies simultaneously. But you have to ensure the grenade takes everyone out, otherwise all you do is alert the remaining people that got cooked that they are under attack, which will raise them to alert and make it really difficult to sneak some more.

This is not as relevant in this map as the only way to block vision is with terrain, however, if you are playing a different map that has bushes and you have a sniper for example, make sure that if possible he is either prone or crouching inside a bush "concealment shown as cover in bushes" that will make it very difficult for the enemy to spot him and he can take out quite a few people.

For another example or to have a look at how to use the stealth mechanic a little more, you can also view how I played through the first half of the Finnish mission "The Raate Road", here I employed all the things mentioned above, stealth using terrain, bushes, and a combination of knives, grenades and sniping from a bush:

https://youtu.be/8Sb-UEhE9bM?si=2B-CQWwcrks_B1OZ

As for the second part of your question, I'm not sure why the mission auto fails, as far as I know, that should not be happening. Maybe go to main menu and restart the mission from there, sometimes the triggers don't work correct, and then a good old fashioned restart sometimes does the trick.

Hope this helps.