The Tandem t:slim X2 has a cover for the USB port. This cover must be opened and closed on a regular basis to charge the internal battery as well as for data uploads.
The USB port cover seems to stop closing tightly after a period. For us it was about 18 months.
Big deal? No.
Annoying? Yes.
The solution is simple.
Call Tandem Technical Support and report this.
Tandem will send you at no additional cost a small package containing two USB port covers.
These are easily replaceable at home.