light switch sexpert help

[dnsfpl]

my "dual" light switch got a weird issue

switch A off switch B off, light off
switch A on switch B on, light off
switch A on switch B off, light on
the above 3 scenario works prefectly

switch A off switch B on, light off
this 1 light suppose to be on, but not sure why now become off

any sexpert knows how to resolve this weird issue?

 

[C_boliao]

Reconnect your B,

 

[j4jersey.]

my "dual" light switch got a weird issue

switch A off switch B off, light off
switch A on switch B on, light off
switch A on switch B off, light on
the above 3 scenario works prefectly

switch A off switch B on, light off
this 1 light suppose to be on, but not sure why now become off

any sexpert knows how to resolve this weird issue?