Twitter card does not work anymore after a certain time


#1

Hi,

My website http://embedsysweekly.com is validated for the Summary Card with Large Image (As an instance this page http://embedsysweekly.com/issue10-system-on-chip-resistor-nand-tcp/)

When I share my page on Twitter the card works as expected but after some time my cards are no more displayed
For example these tweets :


Is there something wrong with the way I provide meta data or anything else?

Thank you for your help

PS : You could not that @nytimes tweets with cards have the same problem https://twitter.com/nytimes/status/417690018703220736


#2

http://imgur.com/lSJVrer


#3

Sometimes it works, often it does not work. Do you know if there is any problem times to times?