My gameplay time right now is around 50 hours, and there were no sign of mausoleum pieces at all in the last ~30-40 hours. In fact, they only dropped at start of the game. I have 10/12 right now...I don't know what caused them to stop dropping, so yeah...

They will continue until you get the last 2. I'm sure you are looking for rare ones.

That is normal and doesn't indicate a bug. The collectibles appear randomly and only stay on the ground for a short time, and it's unlikely that any player will see, much less gather, every collectible that appears. Some of the mausoleum pieces are very tiny and blend in with the rocks on which they appear, so you have to be very vigilant and observant to see them.

They are not spawning at all. That's the point.

2LadyCFII, thanks for reply, but I've been 9 hours online in a row in game with full control and no sign if single mausoleum drop. I will continue monitoring on this matter.

EDIT: I don't remember exactly, but I think they stopped after stream of life returned to normal.

EDIT2: Wait..does same(old) mausoleum pieces respawn? If no, than it's all fine.

The collectibles are not "scheduled," and there will often be periods of time where one or more types will appear to dry up for a while. Again, this is normal. The collectibles are not intended to be 'easy' to finish, although it's certainly more likely in VV4 than in previous chapters.

Well, they are easy. 3 collections completed in 2 days of real life. Mausoleum right now is impossible to complete because no sign of them at all. I should check my theory of EDIT#2. Then it all will be clear.

I happened upon a very small piece that I would normally have passed over thinking it was a rock because it blended in so well - those last two will eventually show up for you; you just have to be patient it's all part of the game experience - if they all showed up in the first few days I'd be disappointed personally. There has to be some challenge, otherwise what is the point? Have fun, it's a great game

Ok, my last report on this matter.
As I suspected, mausoleum pieces DO NOT re-reswawn(pieces, which you already collected won't appear again).
Lately, I found 11th piece. Now it's gonna be really hard to find last one because of small chances to appear.

No bugs after all.

This ^.

Note that the chance of a given piece is not affected by the fact that the mausoleum pieces are UNIQUE. It just affects the chance of a respawn of a piece you already have (which has been reduced to zero). If the piece you need was going to spawn, it will still spawn.