Weird outlet tester reading on the 110v outlets?

When using a typical 3-bulb outlet tester (Klein RT110) on my EB240, I get a rather unusual reading:
dim/flickering - lit - dim/flickering

For reference, a properly grounded wall outlet would read dark - lit - lit, while an ungrounded inverter outlet would read dark - lit - dark

What’s your reading on your 110v outlet? And what does my reading mean?