Donald Trump (All General Trump Conversations Here) Just as an example, Dutch pension scheme associations (PSA) have invested about 25% in low risk bonds from countries like the Netherlands and Germany and they hold riskier ones as well.
Banks have to hold high quality liquid assets to meet regulatory obligations; mostly leverage ratio and capital requirements. They mostly hold that in bonds as well. So a debt jubilee will wipe out their capital base, making them much less safe vehicles for financing activities in the real economy. So you need to relax those rules or think of something else.
It also doesn't solve, in my view, the resulting inequality of the debt fueled asset inflation. The rich got richer (especially those in the financial industry) and they'll stay rich. The debt jubilee would only solve one part of the equation. As you see in the German example capital has a much lower exchange rate to the DM.
This is all to say that a debt jubilee is a good idea but with resulting problems you need to solve but also with the realisation the existing system that resulted in this situation continues afterwards. A debt jubilee every 50 years is going to create tremendous moral hazard so if you're going to do this, you'd better fix the system in such a way it doesn't happen again.