ouR escaPOD mods

You might find this an interesting read.

Lithium longevity

I wasn't expecting it to. I'm sure there's nothing wrong with the monitor you have. Just pointing out what settings are used to get really precise SOC measurements. A less expensive monitor without all the settings won't be as precise. As I said before, your monitor is only about 5% off right now, that's actually pretty good.

It shouldn't matter. The monitor reads a voltage across the shunt and interprets it as a current flow. Since it is clocking amphours in and out it would need to be disconnected for a considerable time to effect the capacity measurement.

A capacity monitor should be able to use the full charge battery voltage to reset itself to 100% SOC. Otherwise it would build up errors if you were say to cycle the battery between 50 and 80 percent for a long time. By using full charge voltage to reset occasionally it knows that that battery is at 100% SOC. Since Li batteries can have differing full charge voltages does your capacity monitor have a setting where you can adjust that?

A good battery capacity monitor has a bunch of other settings too. Here for example is Victron's monitor setup parameters.

Victron

At the start of your discharge test your monitor thought you had 200AH? Some amphour capacity meters use a moving average approach to determine battery capacity. Effectively they need some cycles to "learn" what capacity the battery has. So they aren't very accurate to start with. A 5% error isn't that much really.

How are you determining when you're at 55%?