Swarm question from newbie

Hey people,
Newbie here,
5 weeks in now with my new hobby. Started with a last season NUC from a friend and transferred next day to full hive, 5 weeks ago. Colony was doing great for 4 weeks. Started to look pretty packed with bees and saw a play cup, so put super above queen excluder to give them some space. They swarmed and returned to hive last Tuesday 11am, then following day swarmed again at same time and returned. About half hour later I spotted my clipped queen on the decking with a cluster around her. I took 3 frames from hive along with 3 new foundation frames and moved these to a NUC with the queen.
Now , here's my problems.
I had a swarm again this Wednesday 2pm from original queenless hive. I had a quick check this morning and the numbers still seem high, so I think they have returned again.
I had only checked both hive and NUC that morning.
Queen is still in NUC, but numbers seemed smaller(maybe foragers went back to original hive?) and there has been no new eggs or larvae, one week in.(She was great in old hive.)
In main hive counted 6 perfectly formed capped queen cells. No eggs or larvae, and 3 full frames of honey? but only 3 of the super frames have any pulled comb, and only about 20% at that.
All normal activity today, and not going to open again for 2 weeks, but I have so many questions, about the swarming reasons???
Can anyone enlighten me as to why, or advise going forward.

thanks in advance.