I forgot to tell, because I believe it’s irrelevant for the situation, that when discharging/inverting and measuring that erroneously -1.3A instead of about -0.7A, the AC-IN is/was disconnected…
You can’t measure DC discharge current based on AC current.
Well… you can, but It’s a very bad idea.
Although I wouldn’t be surprised, considering this: Venus error in computing DC power?