Hi Sam J
First, did you rig it the first time on the sand or did you somehow get sand in the joint the first time you rigged the new TK mast?
The fit of the ferrule on a carbon mast is a pretty close tolerance affair, and if you get any sand in between the male and female diameters, when the mast is bent (like you left in in the shallow "wash" at the edge of the water with the sail rigged) it can be very difficult (impossible in some cases without using some extreme measures) to separate the mast as tiny grains of sand and grit get into the slight opening at the front of the mast (even inside the luff sleeve) and then when you let off the dowhaul, the slight opening closes up and traps or embeds the grit in the joint.
If you have your mast apart, take a bar of soap (plain 'ol bath soap) and rub the soap on the outside diameter of the male portion of your ferrule.
Now put the mast together and twist the top and the bottom sections a few times.
Then take the mast apart and look for dark shiny spots on the male portion of the ferrule.
These are the "tight spots"!
Now take a smooth flat file and gently work the "tight or high" spots down a couple of strokes of the file at a time (just take off the shiny spots so they blend with the surrounding areas of the diameter.)
This should free up your mast, and make it very easy to take apart when it's "clean" and there's no grit in the joint.
To positively "eliminate" this problem, get a roll of vinyl electrical tape and wrap the joint of your mast (with the ferrule tightly pushed together) with a couple of wraps of the tape.
This will exclude any grit and ensure that the mast does not take on any water at the ferrule.
You can use the tape several times if you are careful when you take it off after the mast is out of the sail when derigging.
This process and the "tape trick" have been making my life easier for many years and I sometimes have as many as a dozen mast to take apart at the end of a big demo day.
Hope this helps,