Hello,
If you are sure that balance carry forward is done properly from 2010 to 2014, you can contact SAP for this through OSS message. They may find the exact root cause. We had similar issue where balance in FS10N and FBL* reports was not matching. Issue was due to multiple clearing documents got created in background due to some issue at database level. SAP corrected those documents.
If you are not in new G/L, all backdated postings wont automatically carry forwarded. We have to run balance carry forward programs again. Check from this aspect as well.
Thanks,
V V