Okay, an update from me.. firstly Dahua UK Support have said the camera "sounds faulty" and to contact my distributor for a replacement, I also acquired a used one today and have the two running side by side on the same Dahua NVR. I was also sent a new firmware by them prior to this and the errors I was getting in the log, on the reboot no longer say Reboot Mark: Exit, now it says Reboot Mark: Abort.. and, interestingly, the amount of logging on the used camera is far less than the faulty one..
Anyway, it's going back for a replacement.
The faulty one is running this:
Device TypeDH-SD49225T-HN
System Version2.623.0000000.7.R.R4.2510.9A.NR, Build Date: 2018-11-24
WEB Version3.2.1.662493
ONVIF Version16.12(V2.4.3.580229)
PTZ Version3.02.93.RHNZ_170518_22722
The good one is running this:
Device TypeDH-SD49225T-HN
System Version2.623.0000000.7.R.R4.2510.9A.NR, Build Date: 2018-11-24
WEB Version3.2.1.662493
ONVIF Version16.12(V2.4.3.580229)
PTZ Version3.02.93.RHNZ_170518_22722
I've attached the firmware if anyone is interested, think it's PAL though.