There seems to be a misunderstanding on wire length.
Wire between the dedicated windlass battery and the windlass is #2 AWG for part of its length, and 4/0 the rest. TOTAL length, round trip of positive and negative wires is under 3 metres (say 10 feet, not 100). Assuming #2 wire and 10 feet for 130 amps, calculated voltage drop is about 0.2V
All joints are soldered. All terminal lugs are crimped and soldered. Voltage drop from terminal lug to terminal shows zero under load (my voltmeter shows only down to 0.1 volts)

The wires charging the windlass battery ae 25 feet long, each way. I reckon the battery is limiting its input to the 30 amps I mentioned. It is a new Optima Blue top battery.

After using the windlass with the engine running, and a total of a minute or so at the 180 amp draw, then letting the battery rest half an hour, voltage across its terminals is 12.6V
While supplying the 180 amps to the windlass on no-load, without the engine running, the voltage across the battery terminals drops to 11.3
The battery has an MCA rating of 1000 amps.
Seems the battery is OK to me. What do you think?

to me, a draw of 180 amps at no load suggests a bad motor or serious friction in the drive gears (the main shaft turns easily by hand)