Cat 5e wiring problem

I’ve recently remodeled parts of my home. In the process I’ve added 2 cat 5e runs that run back to my old run.

I’ve tested the run to the old and the old run. They both work separately. However when I join them – I see to lose pins 1 and 3 on the runs – but they work fine when not plugged in together.

I estimate the total length of the runs to be about 100 feet. Im using riser rated cat 5e cable.

Any ideas as to why this is happening?

Thanks!