Assuming the Implicit Context Load is defined either at the Project level, Job level, or through the tContextLoad component on all Jobs. A parent Job calls a child Job, and in the tRunJob component Context Param section, you changed the value of one context variable from the original value of A to the value B.
However, when running the parent Job and checking the context variable value from the child Job, the value didn't change, and still shows the original value of A.
[statistics] connecting to socket on port 3541 [statistics] connected This is childJob CTX_var_1: A [statistics] disconnected
A best practice for this type of design is not to load/set Implicit Context in child Jobs.
Modify the context variables in the parent Job tRunJob, and select the Transmit whole context check box.