It is covered in >>this post<< somewhat.

Thanks for your quick response.

I'll have another look at it and will no doubt be ordering some parts later today.

If the body is wobbly and it cuts out when pulled backwards, then >this< is probably what's causing the wobble. As a result, the male terminals of >this loom< sometimes arc and degrade causing the problem you describe.

If you look down into the neck, if that is the case, you will often see one terminal looks shorter than the other. Or looks sharp and burned.

It can be the bag housing internally at the bottom at the female terminal of >this loom< (where the one above connects to). But very seldom, and you will often see burning if that is the case.

Speaking of the back body, another possibility is will the handle pull out of the back body when the tab is locked? If so, they can crack internally and as you use it, the crack expands, the handle lifts up/out a bit and continuity is lost. In that case, replace >the bag housing body<.

Before suggesting a PCB, which might be a more regular issue, it depends on which one is fitted >the older one< tends to be more reliable than >the later one<. And also, if a PCB, it will usually cut out predictably, such as 10 seconds after starting for example. If it is cutting out randomly in use, and not if left running alone, and especially if pulled back, one of the first issues is more likely.

However, you say you have checked the lead, but if just a continuity test, that often isn't enough. The cable can fail internally just near the cable entry grommet. In that case, you need to power it up, and pull and twist the flex by that grommet slowly and in all directions to see if you can replicate it.

My Sebo X4 is cutting out when in use.  From reading the earlier posts it seems there are three possible causes:

1  Power cord broken:  I've eliminated this.
2  PCBs faulty:  just before it cuts out the two red lights briefly flash on together.  I've read this indicates a PCB problem.  The side PCB shows no evidence of burning or other problems so I guess the top board could be at fault.
3  Physical failure at the junction between the bag housing and the base unit:  it feels like this is the problem: when upright it's mainly OK, when pushing it's not bad but it always fails when it's pulled.  The top part also wobbles a lot which suggests physical wear and tear (I tried to cure this using the Duck tape solution suggested here but no luck). 

I think the contacts must be worn so I need a new top housing and I see you sometimes offer refurbished units.  Do these have new contact sockets at the bottom?  Should the male contact holder in the base unit be replaced at the same time?  Finally, if the two lights are coming on together is it possible that the PCBs are faulty as well as the physical connection?

Hope someone can give me some advice.

I'll talk to you later this afternoon.