Hi avs,
You can see some comments about the layers of the RX300 in posts #1 and #2 here and in post #9 here.
Based on these specs … there are no obvious weak links or low quality materials in this mattress so it may be interesting to see what may be happening.
If you have any other information about the layers in your mattress then feel free to add what you know. It would also be helpful to know your weight and body type and sleeping positions if you are comfortable sharing these.
Other than the difficulty with movement which can be a side effect of memory foam itself (because it is a very low resilience material) … are there any other symptoms that you are experiencing on the mattress (pressure points, back pain etc)?
If you don’t know the depth of the impressions they measured you can check them yourself. If you place a straight edge like a yardstick over the impression then you can measure it’s depth with a ruler or tape measure. This would be a good place to start to see how much the materials have actually impressed and how close you may be to the .75" exclusion.
Phoenix