I have tested the same process through the Windows Console and it works fine. So it only happens when using the Web Console.
Are you entering some data in the column tps_company?
It seems like the company mapped to the 3 users is not available in the list of tps_company. Hence the foreign key constraint error.
I managed to resolve the issue.
As it turns out, these 3 problematic users had designations in the "Company" field that did not match any of the allowed inputs. Once I assigned the user to an accepted Company, everything works.