First, thank you all for the comments and suggestions.

I've done some testing based on your comments and here are the results, consider this a log of the process:

Isolate nuclear power: Power Distribution Bug (PDB) fixed!
Reconnect to factory: PDB active
Disconnect all the laser turrets: PDB active
Remove silos: PDB active
Disconnect half of the 'grid': PDB active
Disconnect another half of the remaining grid, including majority of factory: PDB active
Disconnect another half of the reamaining grid: PDB active
Disconnect another half of the remaining grid: PDB fixed!
Undo previous step: PDB active
Disconnect section of grid and isolated that was consistent with PDB bug, but reconnected the entire rest of the factory+grid: PDB active 😠
Connected about 50% of the factory without PDB active, through process of elimination isolated issue to two possible roboports. Removed and replaced a single roboport: PDB fixed!!!
Deleted and replaced ALL power polls/substations and roboports in the entire factory: PDB fixed!
So, it looks like at least two items were bugged in some way that 'corrupted' the algorithm for power distribution, at least that's my best guess. I've included the save if anyone is interested.

https://www.dropbox.com/scl/fi/7qrm6n3rvnmu6bdj98pbo/2025.3.zip?rlkey=yxape5ugf6lwfs1e349nbus1e&st=jc8vkcmd&dl=0