Slots disappear

After moving an exact same route to a different airline within the holding, and lining up the slots exactly as they were scheduled previously, the new airline no longer has access the the same slot pairs. Even though i had them before, albeit another airline of mine the slot has disappeared.

This is on Devau. Panama Skies.

Why might this be? 

The slot was

1) not released from the old aircraft

2) previously accidentally oversubscribed by system error

3) not released back to pool by system error

#2 & 3 you can check by doing manual slot count. If the slot count is less than the listed number slots per 5 min on airport information page, send email to support to refresh slots.

Please send an e-mail to AirlineSim Support including game world and the airport where the slot problem occurs, and we'll be handling that quickly.

Great. Have sent the email to support now.

option 2 would worry me if this to be the case. How frequent is this likely to occur?

Wow, that was a fast response. Within 5 minutes of sending the email, the slots have now cleared. Thanks!

option 2 would worry me if this to be the case. How frequent is this likely to occur?

I'm not sure this option actually exists - I've never encountered it so far. It's usually option 3 happening from time to time but not avoidable due to performance reasons.

I have had option 2, not much but there were cases, I found about it when trying to swap aircraft and the swap results did error, and upon further investigation I encountered more slots than the limit.