decimal increment/decrement problem

Testing this plugin and having strange behavior with toggling decimal amount at values 1.0, 1.1, 1.2. Step value is set to 0.1, when I click increment from 1.0, it jumps to 1.2, if I decrement, clicking does not allow decrement less than 1.2, it resets the value to 1.2. If I hold decrement, it works. If I manually write value 1.1 and defocus input field, it changes to 1.2. Seems like 1.1 is restricted. I disabled all plugins except WooCommerce and this plugin, swithed to default theme, the problem is not caused by theme/plugin conflicts.