I'm playing version 10.03, going through all episodes in order. In episode 2, if I buy costumes from episode 1 they update correctly in the costume gallery. If I buy costumes from episode 2, they don't update. If I skip ahead to episode 3, the start of the episode automatically loads up all episode 2 costumes correctly.
Missing costumes in episode 2 is only an issue because of Lola's 3rd event, The Ribbon Pageant, which requires the player to specifically load the ribbon costumes on each girl. As far as I can tell all of Episode 2 is playable apart from that event, but I'm just too curious to see what the event is about. Reporting this in case you're already aware of a quick workaround you could share, such as buying costumes in a specific order that I haven't figured out.
P.S. I've been following your work for the past 10 years, feels weird writing to you just for a bug. Your creativity, passion and dedication set you as an example for other creators. Here's to hoping one day you'll be able to follow your plan of attending a great art school, if that's still on your mind.