Which Image?
Which hdd is used?
Format of the hdd?

what do you mean with frozen?
the record ist stopped?

Hard drive in or from your Computer?
connected via LAN or USB?
if LAN: nfs or cifs?

please describe your situation as good as you can, otherwise it is hard to help you

SD-Records are OK?
Only HD has freezer?

Seems that the network-speed is to slow.
Use faster network, or - much better - an local usb-hdd.

My spark triplex makes recordings to a w2k8 server via cifs without Problems ( one stream ist absolutely OK > more ist dependend off the bitrate )
But I´m using Neutrino ( makes no difference whether MP or NHD2 )
I know that some network services in e2 ( media-Portal ) or shitty epg scanning stuff costs memory and system Speed > therefore it´s to poor then for network recording.