If the 3 or 4 cable boxes were exchanged over a long period of time, then you've been very unlucky. But if you exchanged all of them within a short period of time to fix corrupted recorded programs, it's more likely that you have a signal issue. You should schedule a tech visit to check your signal strength, including at the tap. If your cable comes in from a pole, be sure to specify when scheduling the appointment that you need a tech with a ladder.
In some cases after getting an error code 126.96.36.199, after power cycling, I was able to play back a recording, sometimes without issue, sometimes with a skip to end, the most recent a 3 1/2 hour recording that froze up at 2 1/2 hours, that was watched once without issue, then got an error code 188.8.131.52, then the next day it would play but freeze up at 2 1/2 hours. This has been pretty much the pattern with all of the Contour 1 Cisco DVRs we've had.