This sucks, occurs when the heat melts the conductors that aren't potted and fixed to the heater. I find that you can put some high temperature heatshrink around then use waxed fiberglass tubing over each then over the pair. Will dramatically raise the barrier to the short. You will need heatshrinking tube that is stable at 220C, if you cannot source it or don't like the cost, use white plumbers sealing tape. Its much fiddlier to make a good electrical seal but overkill can manage it. It is stable at this temperature and beyond.Lastly if the potting area is small, attaching a heatsink 10mm will greatly reduce the heat reaching the wires.you might have to make a hole in the depending on the space between the heater and the side.
Yep Jeff-o. seen it so many times, its caused by too much heat conducting through the heating elements leads to the conductors of the wires that leave the casing. They are usually potted and have a clamp designed to help sink the heat,, this area can be too small and not enough ventilation so eventually the wires lose insulation and pop. Very annoying to fix since the short will either be in the potting or at point that its difficult to get a hookup to the conductor to the element wire. You cannot solder these, so gotta hook it up and sheath it in fiberglass, bury in epoxy or whatever takes your insulating fancy
Statements over the archival status of an adhesive is rather redundant to be made in passing. The usage of adhesives isn't as simple as stating use a PVA glue which is suitable in most cases for archive purposes. But is doesn't account for the requirements of the object in its lifetime or future manipulation in archive. It is a big topic and one where there exists continued academic and trade level discourse.JDRocker, PVA is a usually a better choice when working with paper and books and likely a safer bet if a book is to exist into the future. It isn't entirely reversible from the paper but it isn't likely to fail either.