It seems to me that you are suggesting it may be an issue with the bed frame rather than the mattress, although you have not advised your body weights or preferred feel.
I suspect that the issue is not with the base, but the tension of the mattresses you are choosing. You have gone from a soft forgiving memory foam to a firm ortho cruz.
The primary consideration in choosing a mattress is the body weight(s) of the people using it.
|Upto 8 Stone / 50kg||Soft
|8-16 Stone / 50-101kg||Medium
|16 Stone / 101kg Upwards||Firm
Please see our article here on the questions to ask yourself when buying a new bed or mattress.
Please call our office to provide your body weights and preferred feel and obtain specific advice as to what may be the correct mattress to purchase.
Kind Regards Gary