When using the map generator, the preset goes to 'Default', when you click on 'Mod settings' in any of the tabs.
Way to replicate, click on one of the presets other than 'Default', then click on 'Mod settings', then go back. You will see that the preset changes, although you don't make any changes.
[0.15.4] - Map Generator
Re: [0.15.4] - Map Generator
Should already be fixed in 0.15.5
If you want to get ahold of me I'm almost always on Discord.