I’m trying to figure out what is going on here, it seems as if either the load or line feed is going into the 4way box in the middle rather than one of the 3way boxes at the ends. There also appears to be a white (neutral?) wire that is capped to itself doing nothing in that same 4way box. At firs…

Pretty confident I’ve figured out the problem. The wire coming out of the bottom of the “side door” switch box was an attempt by someone to feed an outlet from that switch. The outlet did not work (how could it with only one wire attached…) The white wire on the outlet has conductivity to the capp…

Glad you got it figured out. A 4-way leg with power to the 4-way switch box is/was not all that uncommon. You start with a hot and neutral fed to the box with the 4-way switch and then send the switched hot out through all the 3-way switches, where it makes its way switched up to the light, which …