How Workflow can modify the existing records

My goal is simple.

Module A has one to many relationship with Module B.

I would like to modify the fields content in Module B. Then update the exactly same field in Module A, the fields content is the same in A & B( cuz I try to put all related fields in one module so that I can print PDF)

I tried two methods described in the forum. Both Failed.

Method 1, create an extra datetime field in Module B, in the workflow setup, set a condition to compare that extra datetime field with the system generated date modified field.
Reference Link is here

Method 2, make a condition equals to “any change”, and check the “repeated run” yes. I set the module B’s date modified equals to any change in condition, allow repeated runs, Run on All records. In the action section, I choose modify record. The result is The workflow runs infinitely…won’t stop
Reference Link is here

Can you shed me some light, I am doing lots of research, cannot figure this out.

I would like to copy more than one module’s content to Module A in the example above, say, I also have module C, D etc, I check the process audit in the Workflow, it shows when I modify Module B, it triggers the Module C to A workflow and all other similar workflows altogether. How could this happen? :ohmy:

found the issue, i set up too many workflows, one workflow triggers another one then another one…