The reason is NVS2501 cannot support file size larger than 4GB.
Your memory card from GH4 might be formatted using exFAT, and record file size larger than 4GB if you shoot for long time.
NVS2501 has limited support on exFAT and cannot support file size larger than 4GB.
NVS2825 & NVS2801 does full support on exFAT and support file size larger than 4GB.