SE conditions bug explained
You might notice that sometimes SE related packs (for token costs) are available in the store from the very beginning of the SpecialEvent, but later on some Friday they become locked behind conditions required.
It happens due to two (or more) simultenious SpecialEvents. And you have 150+ (or whatever other amount required for packs unlock) conditions in another SpecialEvent.
F.e. HuayraR packs requires 150+ conditions in SE (as you can see on screenshot above), but you already have ~400 conditions in Aperta SE (which started two week earlier). So Aperta SE was running (f.e.) from Aug1 to Aug 21, and HuayraR SE started at Aug14 and running till Aug30. During that period between Aug14 till Aug21 (HuayraR already started, and Aperta not finished yet), you have an access to HuayraR packs.
In video ^^^ you can see that I have packs available with only 141 conditions in SE, but as you can see on the next video - my ApertaSE already finished.
To save access to HuayraR packs - you have to KEEP UNCLAIMED some reward from previous SE. As you can see on video above - I claimed important EIP from the last stage contest, but have unclaimed blueprint from SE conditions (also I still was able to grab EIPs and decal as next conditions rewards).
IMPORTANT NOTE: You can keep any event unclaimed only for 30 days. After that period event will vanish and you won't be able to collect reward (so be carefull if you left contest reward (EIPs) unclaimed.
If you already finished Aperta SE - you can try to keep Sian SE unclaimed
Also it must work well with any "club reward" in SE (i.e. in SE stage 12, if 10 club members win the race - every club member can get 10 tokens) - you could keep it unclaimed and SE also must not dissapear as long as you not collect it (but remember about 30 days period).
Conclusion: if you managed to keep unclaimed some non-important reward (such as coins or few blueprints) - you can hold this SE for as long as possible in case if some usefull SE packs arrive. if you have to keep unclaimed some important reward (usefull BPs, some EIPs) - then please be carefull with them and don't forget to collect them as soon as don't need those conditions anymore.