I have a 35 year old ficus tree, about 7' tall. I knew from past experience they are touchy-if you move them to a new spot or a new room, they can lose their leaves.
When it started happening early this summer , dropping LOTS of green leaves (like 20-30 a day) I got concerned. Although I still did see some new leaves growing. Was it too old? Did it have a disease? Did it need a larger pot? (Probably ). But now within the last month it's stopped, after losing about half its leaves.

I'm pretty sure it's just from rotating it 180 degrees! It's in a north facing window.
I'm hoping this experience may just help someone else.

Ficus aren't picky, just opinionated and quick to show their displeasure by dropping leaves. Rotating won't cause leaf drop but if your tree has always been in the same place and care hasn't changed, look for other reasons that might cause leaf drop.

When is the last time you repotted? A larger pot isn't necessary, especially if you want it to continue to live in the house but periodic soil refreshment is. Old hydrophobic soil will cause leaf drop.

Do you fertilize? If so, with what and how often? Trees, especially trees in pots, don't need fertilizer as often or at the recommended strengths. Once or twice a year at most with balanced fertilizer used at 1/2 or less strength is enough. Nutrient deficient soil will cause leaf drop.

Last spring when your tree had a problem, did you forget to water when new growth was starting? That will cause leaf drop.