OK thanks for that.
This could be a faulty programmer or selector.
If it's the selector, then try rotating it numerous times to try and clean up the connections internally.
It could be dirty connections inside the selector causing the problem.
Unfortunately intermittent faults can be a devil to find and you could end up replacing a lot of parts to sort this out, if you go the diy repair route.
If you are having an engineer in to sort this out then you would have a labour charge before parts cost so whether it's worth repairing or not would largely depend on your interpretation of "economically".
I'd guess a repair cost of around £130 upward for the labour and parts if it's the programmer at fault.
If you use Hoover themselves, you can add around £50 more to the cost as they charge around £90 labour.
If you want to hedge your bets then I'd suggest a fixed price repair.
British Gas have an offer on at the moment where you get it repaired, parts and labour included for £125.
if it can't be repaired, there's no charge.
.Click here for the British Gas offer
If you are going for self repair then you really need to use a megger to check the insulation of the machine and see if it's a faulty heater, faulty motor or faulty pump causing problems with the electrical system in the machine.
It's not uncommon for a low insulation heater to cause problems in the programmer, or any other low insulation item.
If you are able to test the various parts, pumps, heater, wiring etc, then you may be able to narrow the fault down.
Otherwise, I'm afraid it could be a fairly expensive repair, or a fixed price repair.
Hope this helps
Let me know how it goes or if you need more help.