Thought I found a new bug, review existing Bug Reports to find this.
I'll add that #3 above happened to me and that the Trip Planner and Engineer's Report both didn't calculate and were showing 0 (Zero) Delta-V.
This happened while add/removing a Stack Decoupler below my Command Pod and then reattaching the fuel tank and engine to the bottom of the decoupler.
This resulted in the decoupler and the fuel tank and engine being included in Stage 1, which would jettison the engine on launch and activation of Stage 1.
This may be related to the Part-Picker panel you are on at the time, while testing and retesting this, I clicked on the Command Pod part list and Staging "Auto staged" correct when individual picking the parts off the workspace, and not the Part-Picker itself, or a combined part assembly.
"Auto staging" not so Auto
V0.2
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System Information
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Time of this report: 2/25/2023, 14:04:46
Operating System: Windows 11 Home 64-bit (10.0, Build 22621) (22621.ni_release.220506-1250)
Language: English (Regional Setting: English)
System Manufacturer: Alienware
System Model: Alienware x17 R1
Processor: 11th Gen Intel(R) Core(TM) i7-11800H @ 2.30GHz (16 CPUs), ~2.3GHz
Memory: 32768MB RAM
Card name: NVIDIA GeForce RTX 3080 Laptop GPU
DAC type: Integrated RAMDAC
Device Type: Full Device
Device Problem Code: No Problem
Display Memory: 32405 MB
Dedicated Memory: 16191 MB
Shared Memory: 16214 MB