SAT语法题改文章I have become friends with two people who were fun

SAT语法题改文章
I have become friends with two people who were fun to be around,but some part of me sensed that they were not trustworthy.【But then I would tell myself not to be suspicious of people,so I set my doubt aside.】
(D)I set my doubt aside,however,telling myself not to be suspicious of people.
请问原句为何不行...是因为不能有两个连词?