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.
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.