If your RAS climbs while ripping you are feeding the board into the wrong side of the blade.
I do understand the problem with the slop at the post...

I had one that if I got the post adjustment too tight it wouldn't raise or lower but if it had "any" play it would move too much out at the end of the crosscut.
There is a reason that the 90 degree kerf mark in the table ends up getting to be about 3/8" wide over time.

I learned to keep the post well lubed (I should have been using JPW) and keep the gib tight. Then it was important to always lower the head below where I wanted it then raise it up in position. That took care of any possible up and down differences. I have looked at a lot of new ones in stores and never saw one that wouldn't flex a lot if you pulled the saw head out to the end of the cut and tried to move it side to side... The head to top rail is easy to get snug enough but the post clamp is the weak spot. Still they are accurate enough for government work.
It is critical especially when ripping (just like on a table saw) that the head assembly is adjusted so that the blade is absolutely parallel to the fence...
Like many tools they are only as accurate as the operator. Much like a Shopsmith, some guys love them, some guys hate them. I fall somewhere in the middle. My undies just get in a bunch when they are attacked as too dangerous to use at all...
They are a great carpentry tool but are now mostly replaced by the compound and sliding compound miter saws which are much lighter to cart to the job site.
I mentioned the one I had that I had built an 8' table on each side. That gave me about 19' of total table length. It was OK, I had a long skinny shop then.

I could lay a 24' long 2"x6" on that table and saw it in half in the middle and the 2 halves would just lay there with no extra supports. As I said before it was great for ripping big stuff.
Carpenters liked them for making the birdsmouth cut (and similar cuts) on the bottom of rafters. You could cut about 8 or 10 at one time.
I keep talking about managing risk... I expect to be getting in a lot of roof time as soon as the weather breaks. I would rather spend a day ripping with a RAS. I don't really mind climbing until I get on about the third step of the ladder.

Still it needs doing and as I look around I seem to be the only one here to do it. It can be pretty dangerous, especially on 3 of the old barns with steep metal roofs. They are about a 45 degree roof and the lower edges tend to be up about 20'. It's just a matter of managing risk. I have harness and ultra high strength mountain climbing rope for a safety rope and various ladder jacks and roof jacks etc.
That project will be worked into the job mix with felling, loading and hauling timber to cut with my sawmill so I can build 8 more horse stalls.
I also have an ancient small unused one and a half story house that has to come down this year.
I sold a small parcel of land to one of my daughters and now I need to build a small bridge across the creek since I don't have one any more.
I also have about 8 old trees I need to remove a number of good sized dead limbs from. They seem to be a bit up in the air too.
And my 6 horses all are past due for a hoof trim. Now that gets scary at times.
Still, it is all just risk to be managed...
I don't know what the guys that are scared of their shadows will be doing this spring but I am going to be busy.
.