JamMan Solo XT Owner's Manual page 31

When using a slave/master looper setup, if the master loop is ~3 seconds or less and if
NOTE:
pressing and holding the footswitch from a stopped state does not initiate clear on the slave device,
you may need to initiate play then stop (3 footswitch presses) and hold the footswitch on the 3rd
press to clear its loop.
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