confused about power

All of this is to set up some switches for my mom who is bedridden and has little use of only her left hand -- the coiled wire runs from the wall to the rolling beside table (keeping itself off the floor) so I am limited to 4 wires. Your diagram perfectly explains my diode arrangement.

I've not done the decoupling and diode yet - I was waiting to see if I had to have a 1000uf as you had first suggested. I'll try with the 100uf.

The problem is not so much jittering (not staying put once set) but rather that outside power use affects the system. She has an electric hospital bed and when we run it down, that can cause the circuit to switch off the light -- it seems to me that it's not just affecting the shift register or the relays at that point, because the lcd says the switch is off.

Will it be all right to decouple the circuit more than once? I'd like to decouple it for the shift register as well as at the pico.

thanks for that extra code, I'll let you know how it works if I try it.