This is the accused:

By the way, _always_ untick domain reload if you can afford if Unity, it saves hours !

I tried Reddit, StackOverflow, Unity forums, no answers.
In the end the "solution" is simple: you have to create a _new_ async void function on the top level, that will do a await Task.WhenAll(allTasks...) then an domain reload.
Works like a charm ! I can fire 30 downloads and then have everything !

Well, fellow #unity #gamedev, do _not_ attempt to save the AssetDatabase and then exit Unity ! Unity will happily do the two things together and fail, sometimes. You'll have a random crash... (at least in my Unity version, which is 2022.Y)

I was resigned to do just that, but I had a hunch : Unity wasn't _happy_ about something, _after_ the compilation ended. It's when I saw this line:
```
EditorUtility.SetDirty(versionInfo);
AssetDatabase.SaveAssetIfDirty(versionInfo);
```

Yet another potential candidate: we _did_ update the shader in another package. Reverted that too.... Only to fail again after 5 or so compilations... This is were I would turn to bisecting, gradually pinpointing the culprit commit, but I would need to have 10+ compilation for each trial !!!

Immediate suspect was a package that used quite a lot of shaders : "ahah ! here is our culprit" did I thought. I removed the package, pushed... No crash. Cool ! But after ~10 compilations, it reappears ! That's the problem with random bugs: it is sooo difficult to know when they are fixed !

Sometimes it was Deallocate, but most of the time it was related to shader compilation. Of course, if we try it inside the Editor, the game builds fine. After, it builds fine here too... But Unity decides it doesn't want to live anymore after that and triggers a crash.

Alas, at some point, we had failure appearing. What was most enraging is that the build _did_ succeed, but reported failure because there was a crash inside Unity at the end:
```
Received signal SIGSEGV
Obtained 31 stack frames
0x00007ff66e81a360 (Unity) MemoryManager::Deallocate
```

Trying with 'video' as the gif is not playing