That's what I am saying, most "carbon fibre guys" will not be able to fix it. You need to heat up the parent thermoplastic material, and any material you may be adding to it, so that they "weld" together. If it has dried out or delaminated you would really need to make a mould around that area and infuse thermoplastic into the joint to do a proper repair. You can get various adhesives that will bond thermoplastics but that is not really the optimum solution.
There's a guy who pops into work now and again that did a lot of work with Jim Busby on the LTS and LOBO series so ill see if can remember the exact material that they used in the TP matrix and let you know.
I love these frames but I just don't want to see the thing fail on you! Always keep an eye on the interface between the head tube lug and the thermoplastic as that is where they used to fail a lot. I lost count how many we replaced under warranty......with an LTS! You'll notice on the later iterations of the design that the headtube is fully composite and that was to remedy the issue. They were really pushing the boundaries of the technology at the time so there was quite a learning curve. IIRC the first STS series were actually slightly heavier than the LTS!
Another beautiful example of TP is the old Proflex 5500C with Smart Shocks. I still think that thing ius ahead of its time!!
Even today thermoplastic composites are still not widespread throughout the bicycling industry......but I am working on that as we speak!!