resolving Humax 9150T PVR problems

Initial status  Pre-November 2019
UPSTAIRS
PVR1 sn=...00617                      HD = ...4390
DOWNSTAIRS
PVR2 sn=...01135                      HD = ...0465
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22/11 Swapped HD's
- Schedule went with PVR, not HD
- channels selected with PVR, not HD

20/12
 Downstairs  00617 PVR with 0465 disk
HW  Rev 1.0
S/W  1.00.26
Loader  a4.39
Sys ID 3024.0000

UPSTAIRS  01135 PVR 4390 disk
HW  Rev 1.0
S/W  1.00.26
Loader  a4.37      *** only difference
Sys ID 3024.0000

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Skipping occurs on downstairs PVR Now
but only on recently recorded items
Skipping no longer occuring Upstairs.
Skipping defined as playback jumping forward nearly a minute. able to play 'jumped' part if  I rewind to just after the skip started.  The skip is repeateable at the same point always. It seems to occur randomly in the things recorded.

Hypothesis: It is the recording on PVR 00617 that lays down the condition that causes the skip to occur.

What I may do is test whether I can view recording pulled up to PC on my tablet and if so, swap DOWNSTAIRS HD for the spare one that I have.  15-1-20 Can play recording  on tablet.

15-1-20  UPSTAIRS skipping occured once on 1hr program at about min 56

Dug out other HD sn ....6920