Hi Chris,
Thanks for bringing this issue to our attention. I do see this problem here and have notified the development team in this regard. We have logged a bug report Defect# 1478 on this, and will try our very best to address the same at the earliest. You could track the progress of this bug fix at this link below :
Defect #1478 - Issue when RemoveCustomBookmark method is used.
Thanks for your patience.
Regards,
Ebenezer.P