Do you remember to turn the plant regularly? If nor one side will be getting far more sun than the other - this can cause uneven growth and flowering.

i bet thats the egsact reasen moon grower x .

I have several and I deliberately allow them this one sided growth then when in flower I move them to a corner where all the flowers are then on show. They are lovely plants too.

Also, they require short days and long nights to form flower buds. The buds will be delayed or prevented entirely on the side that is more exposed to artificial light.

No problem with short days and long night in Scotland... goes with the season

But only outside! Stay up late to do the dishes, and the poor confused cactus thinks it's summer again!

Well we usually keep our Christmas cacti in the front porch which rarely has any light at night BUT it also used to flower in spring and summer (when we have light for 20+ hours). I decided it was because I would let it almost dry our before watering again. Last winters big freeze killed it off but I've just bought two small ones in bud, will see how they fare.

Summer flowering isn't unheard of, MG, and drought can trigger it. As with any succulent, though, too little water is better than too much water!