Mercenary Fleets don't replenish themselves

[viirinsoftworks]

Before Grand Archive was released, the mercenary fleets were really really useful. Now, I had a 100/100 fleet that I turned mercenary, and they got defeated cuz I used them against the Black Needle. They've been at 30/100 even with 4 'bigger fleet' upgrades for 30 years. I had a second fleet very similar, and chose to not keep renewing their rentals to see if they'd recover while idle. They didn't either.

What's going on?