A problem with pensions in general is that they're very vulnerable to financial shenanigans. The payouts are generally far in the future when promised, and management and politicians are essentially short-termist; they won't be around when the promises come due, so the temptations to promise more than can be delivered, and to under-prepare for the eventual obligations, are both strong.
There have been numerous instances in the private sector of companies looting their pension funds in secret to prop up their books. This is generally illegal, but it still happens. Public-sector pensions are generally (and shockingly) less-regulated than private ones, and politicians tend to be a little more corrupt when it comes to these things as well. Thus, the problems of over-promising and under-provisioning are rife in public sector pension schemes.
This is made worse of late by the fact that so many places assumed that their investments would yield a guaranteed 8% return on average over the medium term. Evidence has piled up that this is not possible in the current economy, and in fact the pressure to obtain such results placed on money managers have a lot
to do with the financial problems of the last twenty years.
They're largely responsible for the technology stocks boom in the 1990s and the 2000-ish crash, and they're also responsible in general for the financial industry taking more and more risks from the 1990s onward, with a huge rush of pension and retirement savings income chasing returns that they could no longer get safely — but the financial sector is great at convincing itself it's found new ways to get outsize returns without increasing risk. There is no such thing. Thus, the tendency towards derivatives and other exotic financial instruments, and the boom of mortgage-backed securities etc. And we all know where THAT ended up.
A brighter future for a darker age.