So when I got my bike, checking the r/r found it was overcharging. I switched to a shindengen mosfet regulator off a fjr1300 from ebay and that worked great for a year or so, until I found my bike having weak crank etc caused by lack of battery power (jumping with a car battery worked fine)

using a multimeter, i found a .5 amp draw. That would do it! Unplugging the r/r and there is no more draw. Switching to my original overcharging r/r and the draw is under 0.05 amps.
Unfortunately it seems this long term draw killed my cheap caltric battery, so I got a new caltric battery to put on. However, I think the drawing problem not going away has killed that battery too. I can charge it up fully and crank it for about 5 seconds before the battery is completely drained again, not expected behavior I think.

so, 2 more oem shindengen mosfet regulators from newer bikes (one being a mid 2000's r1, other a 2020 cbr650r) later and there is still a leak there. Am I diagnosing wrong? Am I getting just **** parts from ebay? Is there a decent aftermarket r/r I should be using (I don't trust 30 year old stock parts when they were a known weak point on the bike even back then). Does the mosfet regulator have some sort of 'charging' phase to store some sort of reference voltage and my battery is the problem?