PBT environment was already initialized for group

What causes this issue?

The system tried to initialize the environment for processing parallel
RFCs using the function module SPBT_INITIALIZE. Here it was determined
that the environment has already been initialized. This is a
development error in an application program that uses parallel RFCs.
You can find the name of this program in the ABAP call stack.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Report this error to the person responsible for the application
program.

Error message extract from SAP system. Copyright SAP SE.