RHB fund managers are well known for this. Couple of times it has happened, taking risk on riskier bonds. Iianm, 2017 or so.  Well could be opportunity for some

This is true but when we dig deeper into the fund's profile like RHB Income Fund 2, the following is noted:
What we can deduce from RHB Income Fund 2, it's for "conservative" investors and the fund need only to outperform the benchmark, which is RHB's 12 months FD rate.

When Bonds go bad, its pointed out, hey tough luck, high risk, high return.

Investors invest using unit trust vehicle because (reasons) and these funds are in turn actively managed by fund managers in line with the objective, strategy, limits and restrictions. So the question begs:

1. was the fund manager and credit analyst asleep at the wheel?
2. was the write-up in the prospectus just for show?; or
3. other reasons?

Had a quick look at the interim report for RHB Income Fund 2 -FYE 30/9/22 (https://rhbassetmanagement.rhbgroup.com/myinvest/client/funds/fund-info?ipdFundCode=INCOME), it is noted that 2 bonds rating were deteriorating. Prior to the deterioration, the bonds may have an acceptable rating. However, once the adverse news appeared in the market, those bonds were essentially as good as waste paper and it was not possible to dispose.

There are also other vitiating factors as well, sweetheart concession deals that were made with the previous government and subsequently taken away by a succeeding government or covid19 had reduced the traffic flow of certain highway that it has caused cashflow issues for certain companies to service their bonds.

There are bonds that are plague by issues that are beyond their contemplation/control and there are others that are downright illegal... the "S" company. 

No doubt it is the job of the fund manager is to take reasonable risk to get the desired return but there are just circumstances beyond their control. In any case, I would reckon that fund managers and credit analyst should run a more rigid screening and due diligence process to ensure defaults are mitigated. As managing funds is not a short term sprint but a marathon.

Way different from KWEB saga 🤦‍♀️ as the KWEB is totally out of the fund manager hands unlike these which are still in their palm