I'm not sure this question is allowed to be asked here, and I'm pretty sure it's a fault with the game I'm playing but...
I'm playing this game that came out in 2015 called Party Hard on Ubuntu 22.04, but whenever I click on Additional Levels,

and click on the Subscribed tab,

it unsubscribes me from ALL of my subscribed levels, and the tab shows up empty.
If I go to a level, on the Steam Workshop site, that I know I 100% subscribed to, it'll show that I'm unsubscribed.
It could be a Steam issue or a game issue but it gets annoying. Every time I go to the main menu and then back to that Additional Levels tab, it unsubscribes me. When I restart the game, it unsubscribes me. I can't play workshop levels at all unless I click on one and then press Play, to which it forces the game to subscribe and download the level (but then it unsubscribes whilst I play)
So, my question is: How do I stop the game from doing this? The delete download cache button in Steam Settings did nothing and I have restarted the game, Steam and my PC. It is a Linux-supported game so there is no Wine (although I did try Steam's Proton but it only made the game crash when I press Play in Steam).
I don't think the game gets updated anymore, but I have sent them an email via the support tab, which surprisingly has Party Hard 1 and 2 listed under the Game tab.