The United States government sought to convince Taipei to reverse the contract award to Siemens but was presumably unsuccessful.

[7] Following the traction system replacement of the Red line's C301 between 2012 and 2017, the C321 is currently the only train on Taipei Metro to use GTO–VVVF inverters for its AC motors.

As the C321 trains have been in service for over 20 years, the TRTC announced the tender for the first time to propose their second traction system replacement together with the C341 in February 2021.

As with the C301 trains, the Passenger Information Display did not show the doors opening and closing or the time prior to the refurbishment of the sets.

In the case of the Xiaobitan branch line selective door operation had to be used and one half of the trainset used had to be sealed off from public.

The Taipei Metro C341 was developed directly from the C321, using IGBT–VVVF inverters for its AC motors, for the Tucheng extension of the Bannan Line.