I have done a quick search on here but cannot see anything specific to my issue.
I noticed a couple of days ago I was getting slight mosaicing for no apparent reason. Ignored it. Last night no ITV at all so attempted a retune. Next thing get the invalid postcode message but noticed signal was going from good to 0 in a constant cycle meaning that unable to get a good connection to do reset.

Disconnected the Humax and connected an old Goodmans HD freesat single tuner which worked perfectly so eliminating wiring and dish from the equation. Took it up with Humax who conclude it is a faulty box but have not offered to assist n any way. Not impressed at all -box is about 2 years old. Have seen some posts on here about changes to satellite settings recently. I assume this can have no bearing on the issue.

Any views appreciated - not good PR for Humax if it is a faulty box.

ITV had a major failure last night affecting all satellite users and Virgin cable so that is not related.

Your reset problems are likely to be dish/lnb alignment or cabling issues.

Using the manual tune option check what signal you have on 11427 (11428) H. This is the Freesat home transponder without an acceptable signal you won't be able to do a reset.

Thanks Graham - but why would the Goodmans Freesat work fine when the Humax does not please?

After 2 days with unit switched off I reconnected the Humax today and it is working fine at present. Will keep an eye on it now.

I did switch off at mains when it first went wrong but it did not have any effect. So not sure why disconnecting from mains and leaving it should make a difference.

Possibly static build up, disconnecting from mains for a while makes it go away.