Can’t get 2 TX134 remotes to work

1remote takes the program and works perfectly . When program the 2nd remote , the first one quits working . Erased the programming several times and get the same results every time . Am I doing something wrong ?

Hi,
Can you please first check if the programming step is as described in video below?

If still have problem, then I guess there might be something wrong with the receiver’s memory unit.
In that case, please return the unit.

Thank you for your time.