May be this is because of leading zero?
acquiring:
bic: 044525266
in yaml is loaded through
@Autowired
public AcquiringService(
...
@Value("${acquiring.bic}") String bic,
...
)
The Spring Boot version is: 2.1.8.RELEASE
It uses library org.yaml:snakeyaml:1.23

As you've pointed out, quotes fix the issue. The reason can be found in the YAML 1.1 spec.
In YAML 1.2, octals use
0oinstead of0.So
044525266in octal becomes9611958in decimal.For correct usage is should use quotes