2 way light switch problem after building work

[EFLImpudence]

Bugger, it's just come to me.
I was mixing up which diagrams were how it is supposed to be and which were the faulty ones.

So, only ONE wire in the wrong place in the junction box - there was no need to move the blue SL.
I suppose this unknown JB could be the ceiling rose.

 

[Mikefromlondon]

Well done at last you got it sorted out that is the main thing.
Now it is not surprising how and what can go wrong by swapping wires, if you take each switch it has 3 terminals com, L1 and L2, and 3 wires, this alone can give you 6 permutations, combine that with 6 permutations of the other switch you get 36 different combinations, that can produce many different patterns, albeit some patters will be repeated and exactly the same.

going by Bernards corrected diagram,

It was correct as a two way circuit to begin with,. I modified it to be as you described the change which meant it was no longer a two way circuit but simply two switchs in parallel. Either switch down would put the light on

up up OFF
up down ON
down up ON
down down ON

Bernard, thats right, I wanted you to redraw your diagram such that it replicated the above logical states, (The logical states of his present problem) and that is why I asked you to do that, hence I called it corrected version to replicate his present fault situation, to see how far adrift his wiring might have been, but by all means this didn't imply that it is how a 2 way circuit should be.

If you now consider we have 3 terminals in each switch, and 3 wires in each switch, this can give you a combination of 6 permutations within one switch, so when you multiply that by 6 permutations in the other switch you have a total of 36 permutations though some of these will result in repeat pattern or logic, but connections wise you have 34 ways in which one can wire the two way switch wrongly, there are two or may be three ways you can wire it correctly.

 

[Mikefromlondon]

Bugger, it's just come to me.
I was mixing up which diagrams were how it is supposed to be and which were the faulty ones.

So, only ONE wire in the wrong place in the junction box - there was no need to move the blue SL.
I suppose this unknown JB could be the ceiling rose.

Don't worry mate, as I said the number of combinations for the switches to be wired incorrectly are 34, and only 2 combinations will make it work as it should.. certainly a head spinning exercise, I did it out of interest despite I have an urgent 2k job needed badly, I abandoned it for this rather challenging brain teasing quiz.

 

[EFLImpudence]

I did get really confused by this one. Shall know next time.

 

[Mikefromlondon]

I did get really confused by this one. Shall know next time.

Yes it certainly was head spinning, I couldn't proceed with my urgent job as this kept distracting me, unable to concentrate on the job, and I was not getting anywhere, in the end I had to replicate a little rig, using a small 9v battery and two switches, an led, and yes I managed to replicate Bernards layout and by swapping wires in just one switch it would give you the same logical conditions OP was having, and swapping wires in the other also gave the same logical states, so both switches needed swapping wires over. (I made this little rig to draw the truth table for all 36 combinations as doing on paper meant drawing 36 layouts and that would take far too long and do my head in)

So all along we were about the possibility of a short smewhere, but on a perfect layout, a short circuit can cause the same symptoms, so that cannot be ruled out, and so on, but there you go, I worked out there are 3 combinations that will work perfect, an ideal layout is that of Bernard, where each switch will have a switched live, and one can wire two lights from each switch to its own lamp holder (ceiling rose) . It was an interesting learning experience. I can now rest my brains and get on with my job, thanks for your input and together we can resolve issues rather than defame each other.