Problems.

Maintenance costs are relatively small. You can hire another pricey custodian, or remake a building from the ground up.

Domain Specific. Finance tends to require truly accurate floating point math, which can be achieved with modern languages, but is not intrinsic. All it takes is one junior to cause a very bad day.

Security concerns are large. Java is a language not known for it’s safety, stability, nor native performance. No offence to anyone who likes Java.