There is also a chance you succeed and begin walking to the direction past the fence.
You can basically ignore the fail chance by spamming the climb command until you succeed.
Obviously there is the rule 4.A no command stacking.
However, the speed of spamming a command is subjective to players.
To remove any such ambiguity and create fairness…
I would suggest:
Add a timeout/delay when a player fails so they can not climb again until the timeout finishes.
Advanced suggstion:
Based on stats, the timeout might last a duration based on ability to regain composure, maybe they fell from the fence.
Maybe add more flavor the fail message if this is added.