Approximately a week ago, there
For those unaware, On-Track missions require you to play tanks up a single tech line and collect exp. This exp is collected in a mission requiring 25k per iteration, and completing 4 or 10 of these iterations nets you some bonus reward. Thing is, getting 250,000k experience takes time, patience and a bit of good luck – something that the weekend certainly could offer most. Fortunately you could (if you really wanted to) grind this all out in one go OR spread the missions out. This no longer appears to be the case.
On-Track Missions now reset daily and can only be completed once per day. This sort of ghosted-in patch for On-Track missions will make it infinitely harder for people that A) play during the reset timer and/or B) can't play WoT for 10 separate days over the event duration.
I personally was several missions in with the goal of busting out at least 5 of the 25k chunks very quickly over that weekend. I soon discovered that it was now made impossible to do so after that weekend because of this cap and the fact that I had missed said weekend.
TL;DR On-Track Missions reset daily if not completed AND can only be completed once per day. Nobody has yet, to my knowledge, been compensated for this.