The Firewire situation might fix some issues that you are not aware of. The sample rate might be stable with the correct chipset. I wish that PT10 would let me change sample rate in the hardware window...
To get your correct sample rate you will have to go through "the routine" Which will include some restarts. Once you are in, there is the possibility of seeing the now infamous pop up window that states that your sample rate has changed and PT must be restarted. This happens randomly and without operator error. I have now identified this as an Easter Egg from Avid to remind you that you are using 3rd party gear!
The Pres are good! I love the color of the Liquids. I could care less if they are close to the brand name. You can use them in your session with great results. I think that the LS56 is an amazing piece of gear for the money. 10 years ago I could not imagined a box at this price that sounds this good. I have recorded some great sounding songs with my setup.
Pro Tools is a journey, You will need patience and time to be successful with this DAW. It is not plug and play!
I can confidently say that your configuration is the issue not the device.
If you want to see your LS56 work with little of zero issues, download the Studio One demo. It works at a near flawless level which will show you that it is not the device that has the issues, it is Pro Tools.
My own beliefs with PT, (it is like a faith) is that Avid has been downsized to the point that many fixes on the list will never be addressed in my lifetime. I have been in that situation in various companies, when you get to wear extra hats at the same payroll. I have respect for the people who made the cut at Avid.
3rd party hardware is not at the top of any list. I also think that the original code for PT is still the backbone of the program. It really could use a refresh.
I may incorrect, not throwing rocks here.
I do think that there are issues with all third party hardware and PT10, no matter what your might read from an owner of competing brand.