In all the games before this MM quests where rather sparse, and only happened when I talked to Preston (before taking the Castle), and very rarely after taking the Castle. I do not see this as a bug, but it is highly unusual, never had it in this intensity before.

And I just took the Castle, and the moment (really seconds) I connected the transmitter to its power generator I received two new MM quests (two settlements with troubles, both of them new).

Every time, I had now around 4 such quests, nothing from other settlements. While working normally, suddenly every time I arrive in Sanctuary a settler has a 'Raider Trouble' quest for me.

What I see: Now - in contrast to earlier games - Minutemen quests seem to have lost their 'stopgap'. I finished Automatron and Far Harbor DLCs. I started a new game, no save in the folder, with this setup. I use the latest patch and the latest UFO4P (2.1.1). Just a small observation, probably not a bug: Vivid Fallout - All in One - Best Performance.esp I use latest 2.01 version and I try disable UFO4 and talk Arron,Shelbie,Maddox not working but Katelyn work 2 type disable and enable UFO4

Make sure you're using the latest version. That bug was already fixed in a previous update.

Disabled mods fallout 4 latest patch