T21P E2 "locks" or gets very slow

[Willian]

Hi guys,

I'm having an issue on the Yealink T21P E2, the phone sometimes doesn't work right, the phone "locks" or it gets very slow (when pressed some key the phone show the numbers in its display very slowly) and it's not possible to used it, if there is some call in this moment it is interrupted.

I've been testing and noticed that problem happens when phone is long time on, and after to restart the phone back work right.

If anybory there is any procedure, please indicate me.