E12 on the Beko B3WFU48215WW ES indicates possible water inside or underneath the machine. If there is a visible leak, turn off the water taps and request service.
External inspection
The manufacturer documentation says to request service if the condition persists or a hose leak is observed. From a dry area, check where the water appears: inlet connection, outlet, filter, or base of the housing. Note the cycle stage.
Disconnect only if the outlet is dry and accessible. If water reaches electrical connections, do not touch the plug or step through the puddle; ask for help to isolate the appliance. Do not open panels to look for internal water.
Drying it is not the same as repairing it
Removing water from the floor lets you see new leaks, but it does not confirm that the source has been fixed. Do not tilt the appliance or run a test cycle if it is still dripping. The Beko index lets you compare the alert with the documented platform.
If E12 comes from a historical record, distinguish that data from a current leak. A current repeat or an inaccessible source requires diagnosis with the full model; do not extrapolate the table to another Beko.
Record where the water is before drying it, as long as you can do so without approaching a wet electrical area.