Everyone in my squad was maxed except the leader. When I switched leader, I was unable to upgrade the previous leader, the button was grayed out but still showed the cost.

Indeed there is an issue in the code here, thanks for reporting. It will be fixed by next patch.

Hello KingofCharge,

Thanks again for playing the pre-alpha of Comet Force a few month ago! I'm happy to let you know that I have now released a new alpha build directly on Steam, as a free public Playtest. If you give it a shot, I'd gladly read your feedback on the Steam forums!

Link to the Steam page: https://store.steampowered.com/app/2954690/Comet_Force/