Lines get deleted when new lines are applied on the same layer?

For context, I’m drawing bamboo sticks and trying to create the sections you would normally see on bamboo. When I go to draw the section lines on a new stick, the sections I drew on the stick previously all get deleted! I’ve messed around with it a little and its so weird. If I were to draw another section on the same stick all the sections stay (as they should) and as soon as I draw a line anywhere else outside that stick then those section lines all disappear. Also, as the subject line states, these are all on the same layer. Please help!