Hi sorry I was busy with non-3d-related work. I did have a crash in 2.92. I will give it a try again, and I will test 2.93 and see if it crashes. I will be back to you during the next few days!

@Jorge (Newoldschool) Where you able to check if this still occurs in 2.92 or 2.93?

2.92 did not crash.

If some user action changes relations, it is to tag relations for update.

Caused by rB23919d2275f2: Fix T75845: some dependencies update missing when painting textures.

What you call Solution [1] is more correct one. What is confusing about it is the non-trivial condition prior to the tag. It mentions the need to rebuild mesh, but the check only includes curve-based object types. And on top of that some shape and forcefield combination.
It might be fine from code side, but having more comprehensive comment would help here.

Can confirm the behavior.

remove redundant null check

• missing NULL check
• missed building texture for relations as well

missed one case, update incoming

Besides the comment below, this looks good to me.

Re-opening, caused issue which affects more users.

In T84117#1101246, @Sybren A. Stüvel (sybren) wrote:

@Kevin Hays (haysk) converting an object to a mesh may not be the most elegant approach here. What is your use case for this code? Why not use something like a Hook constraint, for example? What kind of object are you converting to a mesh?

@Kevin Hays (haysk) converting an object to a mesh may not be the most elegant approach here. What is your use case for this code? Why not use something like a Hook constraint, for example? What kind of object are you converting to a mesh?

Hello Robert sorry for the delay. I have a new "crash.txt" using the original file, but I don´t have the "debug_output".
But I think that is suddenly fixed.
I will explain it.

@Jorge (Newoldschool) Where the last log files created with a different project? Could you also test if Blender 2.92 that is currently in development avoids these crashes?

@Ray molenkamp (LazyDodo) yes please report that BKE_scene_object_base_flag_sync_from_base issue in a new task. :)

can confirm P1886 fixes the opening post, but not the crash inside BKE_scene_object_base_flag_sync_from_base (P1870) given how "muddy" this ticket is already that should perhaps move to its own ticket?

@Sergey Sharybin (sergey) I tried it with P1886 on master and it works! My crash is gone. Thank you alot!

@Ray molenkamp (LazyDodo), ok, managed to crash. Is trivial, actually: do not de-reference id_orig, store the uuid in the IDNode. Mind checking P1886 ?

That hits the same crash in D10077, in void DepsgraphNodeBuilder::begin_build()

void DepsgraphNodeBuilder::begin_build()
{
    // ---8<--[cut unrelated code, it's there just not in this paste]--8<---
    id_info_hash_.add_new(id_node->id_orig->session_uuid, id_info); //<---`id_node->id_orig` has a bogus pointer at this point
    id_node->id_cow = nullptr;
  }