I disagree with the wiki. The real danger with Bristleback is not the combination but transforming him from robot mode to beast mode. I have owned 3 Bristlebacks and all of them combined just fine - the transformation was the real killer.
Bristleback has the problem that the inner tab that causes friction on his legs when you transform him (to keep them in place) is too large and require a lot of pressure for it to move. Skystalker has a similar issue in one of his ship's wings - that is why so many out there have that joint broken although in that case its not due to GPS but for Bristleback this considerably increases the danger of breakage.
What I did with mine was semi transform Bristleback's legs (one piece) and file that inner tab down so that its more manageable and 'softer' to move - Otherwise he can become impossible to transform without breaking. Now I can transform him with no problem at all but I still have to be careful.