Layer Shadow reverts HSBC values on stamps in Fantasy Battlemaps

Using Layer Shadow on Fantasy Battlemaps stamps, which is the default for many assets, reverts the stamp as if all values were unchanged from 0, despite them still being changed.

Only Layer Shadows caused this, normal shadows didn't.

I also tried this on new scenes and old ones and the issue was present in both. As well as other peoples instances of Inkarnate

This is seemingly only for Fantasy Battlemaps, new and old stamps. I tested Watercolour Cities, Fantasy Regional, and Scifi Battlemaps, and found the bug didn't affect them.

Here is the link to the original test: https://inkarnate.com/m/ZRy7Aq

Now here's where it gets even stranger:

Resizing the map fixes this, not only for pre-existing assets but new ones too. Cloning did not fix this issue, only resizing.

Here's a resized map of the original test where for some reason all the test stamps and new stamps are unaffected: https://inkarnate.com/m/vEmyeV