That would definitely explain it. Solid core is desinged to be pulled into walls - It is slightly better at transmitting data over longer distances and is cheaper to produce. It is, however, rather delicate and doesn't work well when in use as a patch cable - It doesn't tolerate the constant bending and changing very well and the strands have a tendency to break.
Definitely go with a stranded-core wire for patch cables, especially if you think you'll need to move them after you install them.
- G