signal problems using UHF/Sat combiners

My sister recently cancelld her subscribtion with sky so, having looked at several videos and doing a bit of research here, i decided to have a go at setting up free-to-air/saorview for her.

She had sky in 3 rooms, one cable to each box. I put in a uhf aerial beside the dish with a 3 way outdoor splitter. I then used 3 indoor sat/uhf combiners housed in a big junction box (3 cables from sat, 3 cables from uhf splitter, 3 existing cables running to rooms). I then split the signals again at each tv using sat/uhf combiners. I used ferguson ariva combo box's. Everything worked fine initially but over the xmas they began working intermitently.

The signal for the irish channels wasnt affected on any box. But the sat signal would somtimes go on one or two of the box's but never all three. then only the sound would go on one somtimes. i checkd the junction box with the combiners and a small bit, not much, of rainwater had found its way in. So i got a proper outdoor 4 way sat/uhf combiner and re-done all connections but the problems persisted. a couple of the box's sat channels were working intermittently and on one somtimes sound went. on one the likes of channel 4, e4, film 4 wernt working but other channels were. then none would work. I checkd the signal level at one of the box's when it wasnt showing the sat channels with a meter which is a basic sat/uhf meter with l.e.d's and the signal had dropped.

Anyway iv decided to do away with the combiners and wire a cable to each box from the aerial so each box will have seperate feeds for sat and terrestrial.

I'm just wondering if anyone could tell me why this might have occoured?

Could it have been faulty combiners?

Maybe the existing cables that were put in for sky wern't capable of carrying the combined signals?

Any suggestions welocome thanks!!