Steam summer sale trading cards issue

Hellow Everybodey!
As you all know summer sale has begun, we braced ourselves etc etc etc...and last but not the least we can obtain summer sale trading
cards by crafting badges or exploring our queue daily. I've gained all the cards I could and crafted all the summer sale badges I could up
to now.
But now, and here's my problem, the cards I obtained since a couple of days are "limited" since they cannot be traded or sold (my
purpose is to trade the dupes to have as I said the complete sets for badges) and the lock will be lifted when the summer sale will be
over and the cards will be expired.
So why I am experiencing this lock on summer sale cards only from a couple of days? (the days before there was no lock since I traded
a bunch of those summer sale cards as soon as I gained them)
And the "Other question" is...am I the only one who have met this issue? .-.
And if you've been so patient and kind to read my little wall of text (and maybe give me a piece of advice if you have a clue about this
issue) you may be interested in a "locomotive driven means of transport" starting from the station fifth letter of eleventh line, seventh letter of first line, second letter of second line, seventh letter of tenth line, sixth letter of first line. And if you're from mobile you can bookmark and wait the moment you're home, I can assure you've plenty of time ;)