Telford tornado hot water spluttering

[Chlopowell]

Hi,
Friday morning our hot water taps started spluttering. We have a Telford Tornado Cylinder which is apparently unvented. We thought it could be an airlock but apparently these types don’t create an airlock.
Does anyone have a suggestions on what we can do?
A plumber has suggested we possibly need to change the valves or something within the cylinder that could have a hole in it. I was just wondering if anyone has had this problem and had a quick, free fix to it.

 

[Exedon]

Find yourself a G3 registered engineer you must have that qualification to work on unvented cylinders.
Follow Telford insulation instructions cylinder must be serviced annually.