The BC Central 20.07.0 release notes (preview edition) states on page 4 that multiple instances of web services may be required to be compatible to all S/D products!
SirsiDynix recommends that customers using BLUEcloud products should upgrade their Horizon/Symphony and Web Services software at least once every year.
Some SirsiDynix products may be incompatible with the latest version of Web Services for Horizon and Symphony.
Before upgrading Web Services, you should verify that other products used are compatible with the new version.
In some cases, you may require an additional instance of Web Services alongside the current version to maintain compatibility with other products.