There is a serious issue here that is not explained by your information.

You refer to a Yale with a capacity of 11500 lb - but that would be at the basic height which could be as low as 110 in (2800 mm). Your forklift has a lift height of 217 in (5500 mm) so I would be surprised if the rating was more than 10500 lbs (you state 11000 lbs). And that assumes there are no attachments fitted to the mast (sideshift or otherwise) as these would reduce the rating further.

You then refer to a Toyota FGU70 (FGCU70?) which has a rating of 7000 kg or 15500 lb, but this is at 3000 mm. My data states the rating at 5500 mm is 14300 lb. And that also assumes there are no attachments fitted to the mast (sideshift or otherwise) as these would reduce the rating further.

I have data on hundreds of forklifts including the Toyota FGCU70. It has a basic safety factor of 41%. So you would have to overload it by 41% in the static situation to cause the steer wheels to lift off the ground. Hence for the Toyota you should find when static that it tips with a load of about 21850 lb.

These units have a forward tilt of 5 degrees. The rating at full forward tilt with the load at 5500 mm would be expected to be about 10100 lb. However it would still not tilt until the load was around 14300 lb because of the safety factor. So that's not an explanation.

If the Toyota forklifts you have will only lift 9850 lb the only explanation would be that either you have a heavy attachment on the forklift, or it's not a FGU70 forklift. My calculations suggest it would have to be a 7FGCU35.

This is a possibility if they had two orders running and the wrong engine covers were placed on the forklift as Toyota engine covers have the rating plates on them.