100 Mbit Ethernet (100Base-Tx) is specified to work on a cable length up
to 100 meters on unshielded twisted pair cable (UTP CAT5 Cable).
But what most forget, this 100 m are splitted up in 90 m of fixed
installation cable between patch panel and wall socket, and 10 m of the
flexible cable for connection to the switch and the device. If you use
normal patch panel type cable with a length longer than 10 m you can
expect problems. I assume the OP has only the flexible cable type. And
if you crimp the connectors yourself you can make a lot of errors.
I myself used 50m flexible patch cable without any problems. Problems
may occur if you crimp them yourself...