UF1 has been tested with popular foot-switches such as the BOSS FS-6 (other brands are available), whose foot-switch behaviour (or polarity as it is often referred to), is a 'normally closed' switch.
In some cases, these foot-switches offer the ability to change the polarity.
Please use a foot-switch designed for 'normally closed' operation and also, to ensure full compatibility use a momentary action foot-switch, or choose a foot-switch that can be set to momentary. This will ensure correct operation with assigned DAW commands.