Tons of problems trying to simulate simple rope without elasticity

[Romahaaa]

The only other thing that comes to mind: is Burst compilation enabled at all?

Oh.. that was turned off at all. Might be after Unity version update settings reset.
Sorry for that, and thanks for your support.

In general weird things happens with Burst settings, I saw many times during developing that rope scene some setttings reset on project open... Googled it, seems it's know issue but nobody fix it for a long time already